trying to create a loop for for opening data files and plotting them

this is the code I have so far. The part in the loop is from code I wrote for just one of the files. I want to change it so that a different file is opened with each loop but i'm not sure how. Thanks for any help

maxit=42;
i=1;
while i < maxit
  A = textscan(fopen('7633_Flux_AmeriFluxFormat_3.dat'),'%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');
  CO2 = A{1,3};
  H2O = A{1,5};
  FC = A{1,7};
  LE = A{1,9};
  ET = A{1,11};
  H = A{1,13};
  G = A{1,15};
  SG = A{1,16};
  WD = A{1,21};
  WS = A{1,22};
  ZL = A{1,25};
  TA1 = A{1,36};
  TA2 = A{1,39};
  RH1 = A{1,37};
  RH2 = A{1,40};
  VPD = A{1,42};
  SWin = A{1,52};
  SWout = -A{1,53};
  LWin = A{1,54};
  LWout = -A{1,55};
  ALB = A{1,50};

    figure()
    plot(x,CO2)
    legend('CO2')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')

    figure()
    plot(x,H2O)
    legend('H2O')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')

    figure()
    plot(x,FC)
    legend('FC')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')

    figure()
    hold on
    plot(x,LE)
    plot(x,H)
    legend('LE','H')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')
    hold off

    figure()
    hold on
    plot(x,G)
    plot(x,SG)
    legend('G','SG')
    hold off

    figure()
    plot(x,WS)
    legend('WS')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')

    figure()
    plot(x,ZL)
    legend('ZL')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')

    figure()
    hold on
    plot(x,TA1)
    plot(x,TA2)
    legend('TA1','TA2')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')
    hold off

    figure()
    hold on
    plot(x,RH1)
    plot(x,RH2)
    legend('RH1','RH2')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')
    hold off

    figure()
    plot(x,VPD)
    legend('VPD')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')

    figure()
    plot(x,ALB)
    legend('ALB')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')

    figure()
    hold on
    plot(x,SWin)
    plot(x,SWout)
    plot(x,LWin)
    plot(x,LWout)
    legend('SWin','SWout','LWin','LWout')
    datetick('x','dd-mmm-yyyy HH:MM:SS','keeplimits','keepticks')
    hold off

    i=i+1;
end

[Stephen23]

From your indexing

CO2 = A{1,3};
H2O = A{1,5};
FC = A{1,7};
LE = A{1,9};
ET = A{1,11};
H = A{1,13};
G = A{1,15};
... etc

it appears that you want lots of named variables: perhaps a table would be easier, via readtable.

[Susan Santiago]

it won't let me upload a .dat file but after the first line, it appears in the workspace as a 1x55 cell. Not really sure how to describe it but it's not just one line of data

[Stephen23]

"it won't let me upload a .dat file"

Append '.txt' as a new file extension, then upload the .dat file by clicking the paperclip button.

What MATLAB version are you using?

"I want to change it so that a different file is opened with each loop"

Please explain about the filenames: are they sequentially numbered? Or do they have random numbers? Or no numbers at all, only letters? What order do you want them loaded in? Are they all in one folder? Are they the only .dat files in that folder?

This is important information: we can easily tell you a method using dir that will read any random .dat files from some folder, but this might not gives the files you want and probably not in the order that you need. The better you can explain the filenames, the the more likely you will get the results that you are looking for: it would help is you gave a few example names, in the order that you want them loaded in.

[Susan Santiago]

2016 but I uploaded the matrix so you can see where those variables are coming from since you asked about it

[Stephen23]

@Susan Santiago: thank you for uploading the file, that helped to understand the data.

Please also explain a little bit about the filenames, as I asked in my last comment. Your question is about how to read multiple files, and we have many choices for how to do this, but which choices are suitable depends on what you tell us about those filenames. Please check my last comment.

Answer 1

[Stephen23]

"I want to change it so that a different file is opened with each loop but i'm not sure how"

By following the guidelines in the MATLAB documentation:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

So you could either use dir to read the names from a folder, or generate the names using sprintf. Pick whichever works best for you. Here is an example with sprintf:

opt = {'Delimiter',',', 'Headerlines',1};
fmt = ['%s',repmat('%f',1,13),'%s%s',repmat('%f',1,29),'%s%s',repmat('%f',1,8)];
for k = 1:41
    fnm = sprintf('7633_Flux_AmeriFluxFormat_%d.dat',k); % I had to guess the name format
    [fid,msg] = fopen(fnm,'rt');
    assert(fid>=3,msg) 
    A = textscan(fid,fmt,opt{:});
    x = datenum(A{1,1},'yyyymmddHHMM'); % simpler
    ...
end

Note that you did not give any information on how the files names change, so I just guessed that the numbered suffix increments each time: if the names have some other pattern, you will have to specify that yourself, or give us a precise specification, or use dir.

Calling fopen directly inside textscan is an inspired move, but is not recommended: MATLAB does not automatically close those files, so you will end up with a large number of open files, which is not a good idea (it can even crash MATLAB if there are too many). So you should always use fclose if you fopen any file.

Note that your code could be significantly simplified by using readtable.

[Susan Santiago]

the names of the files are similar to '7633_Flux_AmeriFluxFormat_3.dat' the only change is the last number changes from 0-4. a lot of the files have the same name though so they're saved as things such as '7633_Flux_AmeriFluxFormat_2 (1).dat' also but the '7633_Flux_AmeriFluxFormat_.dat' part remains the same in all of the files

[Stephen23]

To get those files in numeric order you could download my FEX submission natsortfiles:

https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort

There are plenty of examples in the help, in the HTML documentation, and in the online description.