Convert workspace of cells to double

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sc1991 2018-1-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/376319-convert-workspace-of-cells-to-double

编辑： sc1991 2018-1-10

Hi I have a workspace which is full of cell arrays I want a way which can change the entire workspace to double array.

rite now my workspace is small so i am able to use cell2mat(variable name). But there is a good chance it will increase in the future. Can anyone help me with it.

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sc1991 2018-1-9

编辑：sc1991 2018-1-9

在 MATLAB Online 中打开

So this is my code.

 clc
clear
[~, ~, raw] = xlsread('varnames.xlsx','Sheet1');%varnames is the name of the Excel doument which has real name and alias name column
AllAliasPara=raw(2:end,1);
Realparam=raw(2:end,2);
RealParaIdx=find(cell2mat(cellfun(@(x)any(~isnan(x)),Realparam,'UniformOutput',false)));%Sometimes you have an Alias name but you don have a real var name so the real name row gets a NaN
AliasParaAvailable=AllAliasPara(RealParaIdx);%Available alias name 
Realparanameavailable=Realparam(RealParaIdx);%Available Real name 
xlswrite('Realparanameavailable.xlsx',Realparanameavailable);
[mydata, myheader] = xlsread('Realparanameavailable.xlsx');
[~,~,raw1]=xlsread('dataset.xlsx');
ii=0;
for iii=1:length(AliasParaAvailable)
     colnum=strcmp(AliasParaAvailable(iii),raw1(1,:));
     dataset=raw1(3:end,colnum);
     mydata=dataset;
     ii=ii+1;
         for ii=ii
            commandExec = [myheader{ii}, ' = ', 'mydata(:,', num2str(1) , ');'];
            evalin('base', commandExec );
         end     
end
clearvars ii iii colnum dataset raw raw1 commandExec mydata myheader AllAliasPara Realparam RealParaIdx AliasParaAvailable Realparanameavailable

and the following are sample Excel documents I have created

Real Name  Alias Name
 Temp            _TEMP@
 Engine_Speed    _ENGINE_SPEED

This is the Excel sheet Varnames.

_TEMP@  _ENGINE_SPEED
deg C  rpm
35  700
36  800
37  850
40  900
This is the Excel sheet Data set.

My task is to take the data from data set Excel sheet and use the varnames Excel sheet to get the correct names of the Variable and store the value in it.

This is the code I have been working on. I am sure there is a much better way but rite now as I lack my knowledge in structures I can only think of using eval.

Another concern is by using the above script i get all the variables as Cell and for me to work on them any further i need to convert them to double. I am not sure how to do that.

I have read your comments but I am still not clear how to do it. So please suggest what changes i need to make.

Stephen23 2018-1-10

编辑：Stephen23 2018-1-10

"...rite now as I lack my knowledge in structures I can only think of using eval"

So you want to use eval... and you immediately get stuck on the trivial problem of accessing your data that you can't solve so you have to ask strangers to help you. Do you see the connection yet?

Accessing data is a trivial functionality, it should not cause problems like this. Importing data should be reliable, because the rest of your code depends on it. Why waste time messing around with eval or evalin when presumably actually processing your data is what you want to be doing?

"I am sure there is a much better way"

There are. Perhaps this would be a pertinent time to consider writing better (simpler, faster, neater, more efficient, much more reliable) code?

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

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Answer 1

Guillaume 2018-1-10

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在 MATLAB Online 中打开

We keep on saying that eval and co. are bad practice for good reasons. Yes, it may make it easy to create all these variables that you can easily see in your workspace with recognisable names but ultimately, it just make it harder to use these variables programmatically. As you've found out when you want to convert all of them. So really, don't do it! Ultimately, you'll find that the alternative are easier to use.

Changing your code to create a structure is easy. Replace the code in the (useless) ii loop by:

somestructname.(myheader{ii}) = mydata(:, 1);

However, assuming that you're using a fairly recent version of matlab all your problems (dynamic names, cell array, renaming) would mostly go away if you used readtable to read your excel files:

aliases = readtable('varnames.xlsx', 'Sheet', 'sheet1'); %import alias spreadsheet
aliases(ismissing(aliases.RealName), :) = [];  %remove empty rows (if any)
aliases.importname = matlab.lang.makeValidName(aliases.AliasName);  %actual variable name when imported
opts = detectImportOptions('dataset.xlsx');
[match, index] = ismember(aliases.importname, opts.VariableNames);  %find real name of columns
opts.VariableNames(match) = aliases.RealName(index(match)); %replace column name
if ~all(match)
   warning('Some columns do not have aliases: %s', strjoin(opts.VariableNames(~match), ', '));
end
opts.SelectedVariableNames = opts.VariableNames(match); 
opts.VariableUnitsRange = 'A2';  %to import the unit row
dataset = readtable('dataset.xlsx', opts');  %automatically import with correct column name and type

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sc1991 2018-1-10

编辑：sc1991 2018-1-10

在 MATLAB Online 中打开

clc
clear
[~, ~, raw] = xlsread('varnames.xlsx','Sheet1');%varnames is the name of the Excel doument which has real name and alias name column
AllAliasPara=raw(2:end,1);
Realparam=raw(2:end,2);
RealParaIdx=find(cell2mat(cellfun(@(x)any(~isnan(x)),Realparam,'UniformOutput',false)));%Sometimes you have an Alias name but you don have a real var name so the real name row gets a NaN
AliasParaAvailable=AllAliasPara(RealParaIdx);%Available alias name 
Realparanameavailable=Realparam(RealParaIdx);%Available Real name 
xlswrite('Realparanameavailable.xlsx',Realparanameavailable);
[mydata, myheader] = xlsread('Realparanameavailable.xlsx');
[~,~,raw1]=xlsread('dataset.xlsx');
ii=0;
for iii=1:length(AliasParaAvailable)
     colnum=strcmp(AliasParaAvailable(iii),raw1(1,:));
     dataset=raw1(3:end,colnum);
     mydata=cell2mat(dataset);
     ii=ii+1;
         for ii=ii
            commandExec = [myheader{ii}, ' = ', 'mydata(:,', num2str(1) , ');'];
            evalin('base', commandExec );
         end     
end
clearvars ii iii colnum dataset raw raw1 commandExec mydata myheader AllAliasPara Realpara

This code is just for refrence for anyone who gets struck like me. It was just adding a cell2mat before dataset in this script. However, I would not encourage to use eval as it can end up consuming a lot of your time. So, please invest in structures but just in case anyone is struck and you end up on this page you can use my code for temporary. But, I would strongly suggest to go with the method Guillaume has suggested. Thank you

Guillaume 2018-1-10

在 MATLAB Online 中打开

While we're on the topic of the code you wrote

RealParaIdx=find(cell2mat(cellfun(@(x)any(~isnan(x)),Realparam,'UniformOutput',false)));

This seems aimed at detecting empty rows. Why is there empty rows in the spreadsheet? Ignoring that, the cell2mat would be unnecessary if you hadn't ask cellfun to output a cell array, so:

RealParaIdx = find(cellfun(@(x)any(~isnan(x)),Realparam));

The find is also unnecessary. You can directly use the logical array returned by cellfun as a filter:

RealParaIdx = cellfun(@(x)any(~isnan(x)),Realparam)
AliasParaAvailable=AllAliasPara(RealParaIdx);  
Realparanameavailable=Realparam(RealParaIdx);

Then, I don't understand why you write an excel file ( Realparanameavailable.xlsx) to read it back on the next line.

Then there is of course

for ii = ii

which is completely pointless.

Finally, If you're going to build string by concatenation and conversion, I'd recommend using sprintf:

commandExec = sprintf('%s = mydata(:, %d);', myheader{ii}, 1);

But really, I'd recommend using tables with a code similar to what I've written.

sc1991 2018-1-10

编辑：sc1991 2018-1-10

在 MATLAB Online 中打开

I am sorry it was a very poor code. I did make some change to it. I will post the code for now but I am going to redo the whole code using structure and the way you have suggested.

clc
clear
[~, ~, raw] = xlsread('varnames.xlsx','Sheet1');
AllAliasPara=raw(2:end,1);
Realparam=raw(2:end,2);
RealParaIdx = cellfun(@(x)any(~isnan(x)),Realparam);
AliasParaAvailable=AllAliasPara(RealParaIdx);
Realparanameavailable=Realparam(RealParaIdx);
[~,~,raw1]=xlsread('datset.xlsx');
for iii=1:length(AliasParaAvailable)
     colnum=strcmp(AliasParaAvailable(iii),raw1(1,:));
     dataset1=raw1(3:end,colnum);
     mydata=cell2mat(dataset1);
     eval(sprintf('%s=mydata(:,1);',Realparanameavailable{iii}));         
end
clearvars ii iii colnum dataset raw raw1 mydata myheader AllAliasPara Realparam RealParaIdx AliasParaAvailable Realparanameavailable

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Convert workspace of cells to double

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Convert workspace of cells to double

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