how to populate a cell with a loop

Question

Susan Santiago 2018-10-6

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/422538-how-to-populate-a-cell-with-a-loop

编辑： dpb 2018-10-7

This is what I have with my code so far.

a = dir;
i=3;
d = a(i).name;
A = zeros(40,55);
while i<=43
  A = textscan(fopen(d),'%f %f %f %f %f %f %f %f %f %f %f %f %f %f %s %s %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %s %s %f %f %f %f %f %f %f %f', 'Delimiter',',','Headerlines',1);
  A_time = A{1,1};
  B_time = num2str(A_time);
  x = datenum(B_time,'yyyymmddHHMM');
  i=i+1;
end

I have 43 data files in my folder. when I run this, A becomes a 1x55 cell with data from the first file. I'd like to make it so that the A on the outside of the loop is populated with the cell data from each file folder. Please help

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Stephen23 2018-10-7

@Earlier questions:

https://www.mathworks.com/matlabcentral/answers/421388-trying-to-create-a-loop-for-for-opening-data-files-and-plotting-them

https://www.mathworks.com/matlabcentral/answers/422515-trying-to-store-data-in-a-matrix-using-loop

https://www.mathworks.com/matlabcentral/answers/420395-how-do-i-use-datetick-for-this-code

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Answer 1

dpb 2018-10-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/422538-how-to-populate-a-cell-with-a-loop#answer_340094

编辑：dpb 2018-10-7

在 MATLAB Online 中打开

fmt=[repmat('%f',1,14) repmat('%s',1,2) repmat('%f',1,29) repmat('%s',1,2) repmat('%f',1,8)];   % legible (sorta') format string
d=dir('AppropriateString*.ext');                                  % setup dir() to return the wanted actual files
for i=1:length(d)                                                 % iterate over files found
  fid=fopen(d(i).name),'r');
  A(i)=textscan(fid,fmt,'Delimiter',',','Headerlines',1);
  fid=fclose(fid);
end

Will leave with cell array of one row per file.

Which specific columns are date/time data? The two sets of '%s' I presume?

datenum has been deprecated; better to use datetime instead and easier than textscan would be to use readtable.

Let us know the actual date format/location in the files and we can write specific conversion for it, too...

ADDENDUM

OK, if the string fields are really just 'nan' or variant thereof, use numeric format for them and convert them on input as well.

...
fmt=['%{yyyyMMddHHmmss}D' repmat('%f',1,54)]; % legible format string
for i=1:length(d)                             % iterate over files found
  fid=fopen(d(i).name),'r');
  A{i}=textscan(fid,fmt,'Delimiter',',','Headerlines',1,'collectoutput',1);
    fid=fclose(fid);
  end

using datetime class rather than the deprecated datenum for the date field.

You might also consider readtable depending on what your next step(s) are with these data.

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Susan Santiago 2018-10-7

that's just columns of NAN. The date is written as a number which is why in the code I posted, I convert it to a string and then get the serial date number