searching an array for a value embedded in a string

Question

Stephen 2019-1-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/442110-searching-an-array-for-a-value-embedded-in-a-string

评论： Kevin Phung 2019-1-30

采纳的回答： Kevin Phung

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Probably this is hopelessly simple to solve, but I haven't found the way (being a newbie)

I have a number of large arrays that look like this (a small portion only shown):

I'm trying to find a way to search for and extract the "Pan Scale" value from each array (here, = 2 on line 123, red arrow). This element (Pan Scale) may not always be on line 123, so I can't just search for the 123rd row in all the arrays.

How do I search for the string "Pan Scale" and then how do I extract its value (the number after the equal sign)?

UPDATE: OK, I just found a way to get to the cell in my array (named "C"):

C(strcmpi(C(:,1),'Pan Scale = 2'));

but now, how to extract the value (i.e. here, 2)?

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Answer 1

Kevin Phung 2019-1-29

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https://ww2.mathworks.cn/matlabcentral/answers/442110-searching-an-array-for-a-value-embedded-in-a-string#answer_358551

编辑：Kevin Phung 2019-1-29

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search = 'Pan Scale';
a = C{contains(C,search)} % if C is your cell array, locate index and access cell.
exp = '\d*'; %all consecutive numeric digits
val = str2num(cell2mat(regexp(a,exp,'match'))) 

^ you can use the above for your other elements too, like 'LightControl' or 'PinHoleDiameter,' etc.

documentation:

https://www.mathworks.com/help/matlab/ref/regexp.html

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Stephen 2019-1-30

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Kevin, hopefully you're very patient!

OK, I found a solution and can read in my txt table, but now your code is giving me an error:

opts = detectImportOptions('C:\Info.txt');
opts.SelectedVariableNames = {'Var1','Var2'};
T = readtable('Info.txt',opts);                    % importS the table                 
C = table2cell(T);                                 % convertS table to an array
search = 'Time Per Frame';                         % serch for the entry, Time Per Frame
a = C{contains(C,search)}                          % locates cell in C and access cell.
exp = '\d?\.?\d+';    

Here's what the array C looks like:

I'm trying to find the entry in row 48 (but this row varies from array to array so can't just specify row 48 in my script).

When I walk through the script line by line to isolate the problem, I get this error when I evaluate the next to last line:

a = C{contains(C,search)}
Error using contains (line 40)
First argument must be a string array, character vector, or cell array of character vectors.

Any help on this?

Stephen 2019-1-30

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Wait again...FINALLY solved this mess myself. Primie example of 100 monkeys given infinite time on computers could generate a Shakespearean sonnet!

FYI:

clc;                
[FileName,PathName] = uigetfile('*.txt','Select the txt file');            % select or enter the name of the txt file containing the ImageJ metadata
path=strcat(PathName,FileName);                                            % construct a path for finding this txt file
opts = detectImportOptions(path);                                          % list the options available in this file
opts.SelectedVariableNames = {'Var1','Var2'};                              % choose to import only the columns named 'Var1' and 'Var2'
T = readtable(path,opts);                                                  % this imports the metadata into table T
C = table2cell(T);                                                         % convert table T to array C
search = 'Time Per Frame';                                                 % define the variable, 'search' to = 'Time Per Frame'
a = C{contains(C(:,1),search)};                                            % C is your cell array; this locates index and access cell.
Index = find(contains(C(:,1),search));                                     % finds the row containing the string 'Time Per Frame'
val=C(Index,2);                                                            % creates the variable, val, = time per frame (number in the second column of that row)
scantime = cell2mat(val)/1000000                                           % generates variable, 'scantime', equal to value of time per frame (which is in microsec), in sec 

Probably kludgey, but works.

Kevin Phung 2019-1-30

woohoo!! You can probably condense a line or two, but that's not too important.

now I can finally sleep at night.

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Answer 2

madhan ravi 2019-1-29

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编辑：madhan ravi 2019-1-29

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The below code can extract the numeric digit/s equated to Pan Scale:

r=cellfun(@(x)regexp(x,'(?<=Pan Scale.{0,10})\d{0,10}\.?\d{0,10}',...
    'match'),C,'un',0);
R=cellfun(@str2double,r,'un',0);
Result=vertcat(R{:}) % if you want the result to be a column vector
Result=[R{:}] % if you want the result to be a row vector