How do I apply unique names to structs created in a for loop?

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Scooby921 2019-7-19

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评论： Scooby921 2019-7-26

I have this script and by the end of it I have variables in the workspace containing the quantity and names of vehicle performance modes to be tested, and I have the folder loacations of the data to be analyzed.

%% Initialize
close all
clear
clc
%% Select path and generate list of modes
% Prompt user to identify top level directory for the vehicle to be
% analyzed.
vehiclePath = uigetdir('','Select Vehicle Data Directory'); 
% Extract sub folder names which should identify the number and name of
% various performance modes tested in the selected vehicle. Ignore ., ..,
% and default folder names.
pathContents = dir(vehiclePath);
folders = pathContents(~ismember({pathContents.name},{'.','..','AWD-insert mode name with no spaces-'}));
dirFlags = [folders.isdir];
subFolders = folders(dirFlags);
modeList = {subFolders.name};
clearvars pathContents folders dirFlags
%% List Generation
% List of AWD hardware variants
variantList = {'Booster','Twinster'};
% List of all standardized test maneuvers used for validation. This list
% matches the sub folders contained within each performance mode (second
% level folders named in 'modeList' above).
testList = {'VVT_001 High Mu Path Deviation',...
    'VVT_002 High Mu CRAM',...
    'VVT_003 High Mu Acceleration',...
    'VVT_004 Torque Steer Evaluation',...
    'VVT_005 High Mu Sine Steer',...
    'VVT_006 Low Mu Sine Steer',...
    'VVT_007 High Mu AIT 90deg SWA',...
    'VVT_008 High Mu AIT 45deg SWA',...
    'VVT_009 Low Mu Acceleration',...
    'VVT_010 Low Mu 50kph Tip-In',...
    'VVT_011 Low Mu 100kph Tip-In',...
    'VVT_012 AWD Response Time',...
    'VVT_013 Level Mu Split',...
    'VVT_014 Level Mu Step',...
    'VVT_015 Mu Split 10pct Grade',...
    'VVT_016 Mu Split 15pct Grade',...
    'VVT_017 Mu Split 20pct Grade',...
    'VVT_018 Mu Split 30pct Grade',...
    'VVT_019 Micro Mu Split 50pct Tip-In',...
    'VVT_020 Micro Mu Split WOT Tip-In',...
    'VVT_021 Low Mu CRAM',...
    'VVT_022 Small Ice AIT',...
    'VVT_023 Small Ice DTIT',...
    'VVT_024 Small Snow AIT',...
    'VVT_025 Small Snow DTIT',...
    'VVT_026 Large Ice AIT',...
    'VVT_027 Large Ice DTIT',...
    'VVT_028 Large Snow AIT',...
    'VVT_029 Large Snow DTIT'};
%% Variant Selection
% Prompts user to identify which type of AWD system was equipped for
% testing. This impacts calculations and plots which execute in other
% scripts.
[variant,TF] = listdlg('ListString',variantList,'ListSize',[220,100],'Name','Select Variant','SelectionMode','Single');
if TF == 0
    Err = errordlg('No Variant Selected','Analysis Canceled');
    set(Err,'Position',[600 600 200 60]);
    return
else
end
drivelineConfig = variantList{variant};
clearvars TF
%% User Selection
% Prompts user to idenfity which test is to be analyzed.
[test,tf] = listdlg('ListString',testList,'ListSize',[300 600],'Name','Select Comparison Maneuver','SelectionMode','Single');
if tf == 0
    err = errordlg('No Analysis Selected','Analysis Canceled');
    set(err,'Position',[600 600 200 60]);
    return
else
end
selectedTest = testList{test};
clearvars tf
%% Create analysis path
analysisPath = cell(2,1);
for ii = 1:length(modeList)
    analysisPath(ii) = fullfile(vehiclePath,modeList(ii),selectedTest,filesep);
end
clearvars ii
%% How to use analysisPath and modeList to name the structs, locate the data, and populate the structs in the workspace?

modeList is the quantity and names of the performance modes and these are the names I want to use to define my structs. In this case there are only two, "Fwd" and "Awd". In other vehicle applications there will be more. Other vehicles might have "AwdSport", "AwdOffroad", "AwdSand", "AwdMud", etc.

analysisPath is the file path location to where I need to grab the .mat files and populate the structs.

I'm struggling to sort out the next section of the script. I know I need to run this in a loop, but I can't figure out how to run a loop and output a unique struct name pulled from the values in modeList. I'm also struggling to access the specific data files that I need. This works to access the files contained within the paths defined by analysisPath, but it lists every file and not just the .mat files I'm looking for. Struggling to find the right search terms to find the results I need to push past this.

dir(analysisPath{i})

This is my older script for loading .mat files into a struct. Initialy my scripting was focused around only comparing Fwd and Awd data and didn't allow for additional Awd modes. In this case I could simply prompt the user to select specific data files and then load the Fwd data into a struct named D2 (Data 2WD). I used the same script with F4/P4/D4/etc. to load and store data for 4WD. I know I need to reuse the loop to get the data from the mat files into the structs. I'm not sure how to loop this such that I can populate the struct and then name it for the mode folder from which it populated data. I'd like it to be automated so the naming of folders by users is a bit more flexible. I'm sure it can be done and likely requires a couple nested for loops and maybe breaks and returns, but I'm having a hard time visualizing it before blindly starting to type.

[F2,P2] = uigetfile('*.mat','Select 2WD Data File','MultiSelect','on');
if isnumeric(F2)
    error('User quit')
elseif ischar(F2)
    F2 = {F2};
end
D2 = struct('filename',F2);
for ii = 1:numel(F2)
    Tmp2 = load(fullfile(P2,F2{ii}));
    L2 = [{'Time'};Tmp2.Data_Labels(1:end-1)]; % fix "Time" column mismatch
    for jj = 1:numel(L2)
        D2(ii).(L2{jj}) = Tmp2.Data(:,jj);
    end
end

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Scooby921 2019-7-19

编辑：Scooby921 2019-7-19

在 MATLAB Online 中打开

I guess I didn't realize that this still landed at dynamic naming. Yes the struct names are dynamic, but the data inside them is all the same and should be protected against the next set of data overwriting it. I made that mistake when I first starting learning to code with Matlab (3 months ago). The first thing I found was using the eval function to get my data from the .mat file into my workspace...and as soon as I loaded the second file I realized the issues.

The direction I am / was headed is that the user only needs to identify the top level folder and pick the specific test maneuver to be analyzed. From there the scripts will find the data files, load them into structs or whatever appropriate array, filter, calculate, analyze, store results, and then plot various traces which are important for the selected test. Have my modeList variable lets me add titles to plots indicating which mode is being displayed. Likewise, the selectedTest variable gives me another title string to display in plots or reports.

The base .mat files should all be the same coming from the same data acquisition tool. Obviously the physical values change from one test to the next, but the channel names / field names will all be the same. I wanted to keep each mode / sub-set of data separate to avoid confusion and possible mistakes when I get to analyzing and plotting. It was already a bit daunting to learn and rewrite scripts to go from calling the variable from the workspace to calling by struct, row, and fieldname.

I am worried about the potential mistakes if there is only one struct of data and rows 1-3 are my front-wheel drive data, rows 4-6 are my all-wheel drive data, rows 7-9 are my all-wheel drive sport data, and 10-12 are my all-wheel drive offroad data, and so on. Can I do it this way and just add a fieldname for "mode" and later use that to search for an expression and extract data from this main "load" struct to create the independent ones I'm looking for?

Also...I had tried using

dir(analysisPath{i},'*.mat')

and it spits back and error for too many input arguments. I thought I had commented on that in my initial question submission, but it appears I removed it while rewriting and reformatting things. I tried to read and understand the documentation on "dir", but there was nothing obvious to explain why it won't automatically filter for .mat files this way. I suspect I need another section of code, as I used to identify sub folders, to filter the results down to *.mat.

Scooby921 2019-7-22

Folder Strucutre.png

Guillaume, no, not trying to store the vehicle tests. That's already done. Trying to require as little user input as possible to find specific .mat files, organize it when pulled into the workspace, then analyze it and output results and plots comparing one performance mode to the next.

I've attached a clip / image of my folder structure so it perhaps makes a little more sense, or might help steer the discussion better. Top level folder in the image is "_New Vehicle Test". This is what users would copy and paste to create a new "vehicle" folder. As an example I tested a Buick Lacrosse and thus have a top level folder named "Buick Lacrosse". Within this are my mode folders. In the image there are "Awd", "Awd-insert mode name with no spaces-", and "Fwd". Since we work on active, disconnecting AWD systems there will always be Awd and Fwd modes. It is up to our customer (GM, Ford, FCA, Nissan, Honda, etc.) if they want other AWD performance modes in their vehicles. In a Cadillac XT5 there are 4 modes. In a Jeep Renegade Trailhawk there are 7 modes. The number of mode subfolders is not fixed and because customers don't all use the same names for modes I don't want to make a rigid folder naming structure as what is "AwdOffroad" to GM might be "AwdGravel" for Jaguar Land-Rover. But, below this mode folder level are all of the specific test folders. This structure is fixed. Users will not need to nor should they be editing these names (stuff starting with VVT). These are the folders into which they will store the .mat files to be analyzed.

Scooby921 2019-7-22

在 MATLAB Online 中打开

I wanted to pull the names of the mode folders to name the structs into which I was loading the actual data to be analyzed and manipulated.

At the very basic level my mode folders are "Awd" and "Fwd". I'd have structs automatically generated and named as "Awd" and "Fwd" into which I import the data from the .mat files. If a user adds a mode for "AwdSport", then I have a third struct generated and named "AwdSport", and the data from those relevant .mat files populate that struct.

The names of these mode subfolders are already found and populated in my variable modeList. I feel like I can use those values throughout my scripting to know how many modes were tested and what their names are. Thus throughout the scripting I don't need to call anything by a specific name. I can call it from the character strings contained in modeList. Realistically I don't NEED to have my structs named for the modes. I don't NEED to pull the names from the modeList cell array. I can simply call them A, B, C, D, etc..

I still am struggling to figure out if I can and then how to give the structs different names. Coming back to the bit of code which will read in the .mat data and load it into a struct. Currently I define this struct as "D2" and use a for loop to create the struct, pull the fieldnames from the data file, and then load the data into the struct. In this instance there is one struct and the name is defined before the loop.

D2 = struct('filename',F2);
for ii = 1:numel(F2)
    Tmp2 = load(fullfile(P2,F2{ii}));
    L2 = [{'Time'};Tmp2.Data_Labels(1:end-1)]; % fix "Time" column mismatch
    for jj = 1:numel(L2)
        D2(ii).(L2{jj}) = Tmp2.Data(:,jj);
    end
end

Is there a way to use the same loop to populate multiple structs? Maybe this loop needs to be a function and I need a different line of code to create my structs first? That leaves me still wondering if I can create those structs and name them by pulling values out of my modeList variable.

Stephen23 2019-7-22

编辑：Stephen23 2019-7-22

@Scooby921: Based on your explanation so far, a table would likely be the best solution.

The advice that you are being given in this discussion is valuable, you really should consider it.

"I don't want to store the data in the variable name."

That directly contradicts what you write just a few sentences later: "I was hoping I could pull the names from this cell array and use them to name / define the structs"

Names are meta-data. Meta-data is data. So you are trying to store data in variable names.

The complexity of your folder structure is not really relevant: you can loop over them, or use a recursive function, or use dir, or whatever works for you. At some point you will need to flatten your data (or do whatever to process it), and for that a table seems to be very well suited, just as Guillaume explained. A table makes it trivial to store the imported data and the meta-data (folder names, etc.) together and makes it easy to check which meta-data (folder names, etc.) are present (using string matching, regular expressions, etc.) and therefore run your different analyses (depending on the meta-data) on the imported data. Really, that is exactly what tables are good at:

https://www.mathworks.com/help/matlab/matlab_prog/calculations-on-tables.html

https://www.mathworks.com/help/matlab/matlab_prog/split-table-data-variables-and-apply-functions.html

"I still am struggling to figure out if I can and then how to give the structs different names"

It is certainly possible to do that, but it would not be a good approach to writing code (unless you like forcing yourself into writing slow, complex, buggy code that is hard to debug). Using a table would likely be much simpler.

"Realistically I don't NEED to have my structs named for the modes. I don't NEED to pull the names from the modeList cell array. I can simply call them A, B, C, D, etc.."

If you have a known, fixed number of structures then there is nothing stopping you from hard-coding them before the loops and then accessing them inside the loops. It would be reasonably efficient, if rather verbose code.

"Is there a way to use the same loop to populate multiple structs?"

Of course: define multiple structures before the loop, and then inside the loop use switch or whatever. This would be more complex than just using one table or structure array, but you do seem very determined to do this...

"If a user adds a mode for "AwdSport", then I have a third struct generated..."

This is where your concept falls down: either you can hard-code a fixed number of structures (and easily write efficient, easy to debug, understandable code) or you can dynamically create structures on the fly (and force yourself into writing slow, complex, buggy code). You can't do both.

Guillaume 2019-7-22

在 MATLAB Online 中打开

Looking at the code you use to create your structure, I'd say you could either use a table or a structure. You can easily convert between one and the other anyway. Tables are probably easier to search into and might be more efficient memory-wise (but possibly slower). Using either type of storage, I don't see why your performance mode can't be another field of the structure / another variable of the table.

At the moment, in the field of each element of the structure you're storing column vectors. If you're going to use tables it may be more efficient to flatten that so that each element of the vectors is one row of the table (with duplicated filename and mode). I.e. having this kind of structure:

D2(1).filename = "file1.mat";
D2(1).Mode = "AWD";
D2(1).Property1 = [1;2;3;4];
D2(1).Property2 = [4;5;6;7];
D2(2).filename = "file2.mat";
D2(2).Mode = "FWD";
D2(2).Property1 = [8;9;10;11;12;13];
D2(2).Property2 = [14;15;16;17;18;19];

You'd have a flat table:

Filename      Mode    Property1     Property2
-------------------------------------------
"file1.mat"  "AWD"       1             4
"file1.mat"  "AWD"       2             5
"file1.mat"  "AWD"       3             6
"file1.mat"  "AWD"       4             7
"file2.mat"  "FWD"       8             14
"file2.mat"  "FWD"       9             15
"file2.mat"  "FWD"       10            16
"file2.mat"  "FWD"       11            17
"file2.mat"  "FWD"       12            18
"file2.mat"  "FWD"       13            19

It does store redundant information but it makes it very easy to perform grouped computation (e.g mean of properties per mode). It's just

groupsummary(thetable, 'Mode', 'mean', 3:end); 
%or
varfun(@mean, thetable, 'GroupingVariables', 'Mode', 'InputVariables', 3:end)

Scooby921 2019-7-22

编辑：Scooby921 2019-7-22

As I'm reading up on how to create and use tables I do like the concept of having Filename, Mode, and possibly even Filepath as properties in the table. That will make it easier to identify and then use later. What I'm not finding written anywhere, and I haven't physically played with a table yet, is whether or not I can populate a cell in a table with a vector of data. My properties are going to be vectors of data acquired over time. For all of the data files I'm going to have a Time channel, Speed channel, SteeringAngle channel, and numerous others. For a given .mat file all channels will have the same number of data points, but it's going to be an n x 1 vector of numerical values. Highly unlikely that File1 and File2 and Filen are going to have the same number of data points in the vectors.

Also of concern to me is that my data acquisition tool is inconsistent in its data export structure. See this previous question in which both of you helped me and opted to use the code Stephen suggested. However I get from user providing the top level path to Matlab loading the data into the workspace, I need to make sure I'm accounting for the need to sort and align data vectors with a channel name / fieldname.

https://www.mathworks.com/matlabcentral/answers/454501-how-to-search-for-channel-name-and-numerical-data-in-resulting-struct-after-importing-multiple-data

This is the main reason I was trying to stay with structs. It's what you all first helped me to learn and what I've become most familiar with. Not the only solution, but the only one I've had working to get data into the workspace at any point in time.

I don't want someone to hand me an answer and do the work for me. I want to learn and understand. But...if it helps anyone understand what I'm working with I'm happy to take a folder structure and data and zip it up and attach it. That way if you choose to run any of my existing scripts you can at least point to a folder, have it find data, and see what's going on. Then there are also actual data files to play with.

Stephen23 2019-7-22

编辑：Stephen23 2019-7-22

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"Also of concern to me is that my data acquisition tool is inconsistent in its data export structure."

If your meta-data (e.g. sample channel names, units, data format, etc.) changes between tests, then you really need masssage your data into one common format, e.g. change the channel names to a common naming scheme, etc. You could create a "universal data parser", but that is a monster that you probably shouldn't be fighting. So I recommend that you find out how to make your imported data conform as much as possible to a common template (of names, or whatever other meta-data). This does not mean that every file needs to contain exactly the same data: a few missing channels can be handled easily.

"...whether or not I can populate a cell in a table with a vector of data"

It might be possible (in cell array variables/columns), but I recommend simple "scalar" data in each table element (which really makes tables much more usable).

"For a given .mat file all channels will have the same number of data points, but it's going to be an n x 1 vector of numerical values. Highly unlikely that File1 and File2 and Filen are going to have the same number of data points in the vectors."

You could combine a simple non-scalar structure and tables, to get the best of both worlds:

S = dir(...); returns a structure with file meta-data.
for k = 1:N
    X = load(...); import mat file data
    T = ... massage and convert mat file data to table.
    S(k).data = T;
end

This is essentially the same as Guillaume's earlier suggestion. That the different files have different numbers of samples is irrelevant.

Scooby921 2019-7-22

编辑：Scooby921 2019-7-22

I've already taken care of data channels having different names. One auto manufacturer to the next they will change, but I'm already setup to use calculated channels in the data acquisition tool to rename and convert units into whatever I need for the Matlab scripts to run. I would like to write a script / function to automatically search the data files for specific names and rename as needed to make things work, but that's something for another year...after I understand more about what I'm doing.

The issue in that linked older question / answer is that the data acquistion tool spits out one .mat file with two variables. One is a cell array with each cell being a different n x 1 vector of data, and the other is a character array with each row being a channel name. It's inconsistent in how it organizes the data upon export. That script works to realign the data with the channel name. For lack of knowing another way to do it successfully I've held onto that code and struct generation. Even before getting things into a potential table or struct array or any other variable type I first need to link the names from one variable to the data from another.

Stephen23 2019-7-23

编辑：Stephen23 2019-7-23

"The issue in that linked older question / answer is that the data acquistion tool spits out one .mat file with two variables. One is a cell array with each cell being a different n x 1 vector of data, and the other is a character array with each row being a channel name."

That could easily be converted to a structure using cell2stuct, or a table using cell2table. That does the "linking" for you, and make the "variable" order irrelevant. A table would probably be best.

Scooby921 2019-7-26

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dataAll_structContents.png

Still struggling. I've spent a few days trying to understand tables. I don't understand them. I can't define the variablenames (column names) first and add data second. When I try to add data first and read from a file to populate the table the result is never what I want. Aside from visual organization I don't see the point of the table. If I can't create a table without first having all of my data in the workspace, then the mission is accomplished prior to creating the table. I just want to get all of my data into my workspace.

I've gone back to structs. Using all of my initial code, I've added the following:

%% Populate data struct with mode, filename, and filepath
dataAll = struct;
for ii = 1:length(modeList)
    import = dir(fullfile(analysisPath{ii},'*.mat'));
    for jj = 1:length(import)
        dataAll(jj).mode = modeList{ii};
        dataAll(jj).filename = import(jj).name;
        dataAll(jj).filepath = import(jj).folder;
    end
end
clearvars ii jj import
%% Populate data struct with channel names and recorded data
for ii = 1:length(dataAll)
    Tmp = load(fullfile(dataAll(ii).filepath,dataAll(ii).filename));
    L = [{'Time'};Tmp.Data_Labels(1:end-1)]; % fix "Time" column mismatch
    for jj = 1:numel(L)
        dataAll(ii).(L{jj}) = Tmp.Data(:,jj);
    end
end
clearvars ii jj Tmp L

This works, except that first for loop is overwriting instead of appending. Instead of dataAll having 6 rows, 3 each for Awd and Fwd modes, it just has 3 for Fwd. I know why it is overwriting. It's a for loop and performing the same action twice without being told to index the starting row on the next loop. My brain is just riding the struggle bus this morning and I can't figure out how to fix it. Image attached of the dataAll struct and lack of Awd mode files.

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Answer 1

Joel Handy 2019-7-22

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编辑：Joel Handy 2019-7-22

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Does this help at all? I'm not completely sure I understand the nuances of your question, but If I had a folder structure like you showed in your picture, I might arrange the data something like this. No dynamic variable naming but you can still clearly identify which folders each set came from. You also don't need to worry about folder names being valid matlab variable names.

modeList = {'AWD', 'FWD'};
testList = {'VVT_001 High Mu Path Deviation',...
    'VVT_002 High Mu CRAM',...
    'VVT_003 High Mu Acceleration',...
    'VVT_004 Torque Steer Evaluation',...
    'VVT_005 High Mu Sine Steer',...
    'VVT_006 Low Mu Sine Steer',...
    'VVT_007 High Mu AIT 90deg SWA',...
    'VVT_008 High Mu AIT 45deg SWA',...
    'VVT_009 Low Mu Acceleration',...
    'VVT_010 Low Mu 50kph Tip-In',...
    'VVT_011 Low Mu 100kph Tip-In',...
    'VVT_012 AWD Response Time',...
    'VVT_013 Level Mu Split',...
    'VVT_014 Level Mu Step',...
    'VVT_015 Mu Split 10pct Grade',...
    'VVT_016 Mu Split 15pct Grade',...
    'VVT_017 Mu Split 20pct Grade',...
    'VVT_018 Mu Split 30pct Grade',...
    'VVT_019 Micro Mu Split 50pct Tip-In',...
    'VVT_020 Micro Mu Split WOT Tip-In',...
    'VVT_021 Low Mu CRAM',...
    'VVT_022 Small Ice AIT',...
    'VVT_023 Small Ice DTIT',...
    'VVT_024 Small Snow AIT',...
    'VVT_025 Small Snow DTIT',...
    'VVT_026 Large Ice AIT',...
    'VVT_027 Large Ice DTIT',...
    'VVT_028 Large Snow AIT',...
    'VVT_029 Large Snow DTIT'};
testSets = struct('Mode', {}, 'TestID', {}, 'TestData', {})
for mode = modeList
    testSets = [testSets struct('Mode', mode{:}, 'TestID', testList, 'TestData', [])];
end
for testIdx = 1:numel(testSets)
    % testSets(testIdx).TestData = load(<build up filename based on mode and testID>);
end

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How do I apply unique names to structs created in a for loop?

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How do I apply unique names to structs created in a for loop?

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