Problem appending a variable to an existing text file using save

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Matteo Niccoli
Matteo Niccoli 2015-3-26
编辑： James Tursa 2015-3-26
I have some measurements in a cell array.
data ={...
'AS-01_09' [ 52] [451] [4724] [1]
'AS-01_08' [38.3000] [451] [4724] [1]
'AS-01_07' [ 37] [451] [4724] [1]
'AS-01_06' [23.1000] [451] [4724] [1]
'AS-01_05' [25.6000] [451] [4724] [1]
'AS-01_04' [ 89] [451] [4724] [1]
'AS-01_03' [75.8000] [451] [4724] [1]
'AS-01_02' [49.6000] [451] [4724] [1]
'AS-01_01' [26.3000] [451] [4724] [1]
'AS-02_5' [38.2000] [489] [4736] [2]
'AS-02_4' [ 45] [489] [4736] [2]
'AS-02_3' [44.7000] [489] [4736] [2]
'AS-02_2' [44.2000] [489] [4736] [2]
'AS-02_1' [47.3000] [489] [4736] [2]};
Column 1 has station codes (names), column 2 measurement values, column 3 local X coordinates, column 4 local Y coordinates, column 5 location flag (there are multiple stations for each location).
I also have in a separate cell location names. Stations from the same location have the same location name.
loctns={...
'AS-01'
'AS-01'
'AS-01'
'AS-01'
'AS-01'
'AS-01'
'AS-01'
'AS-01'
'AS-01'
'AS-02'
'AS-02'
'AS-02'
'AS-02'
'AS-02'};
I am trying to separate the measurements by location and save each location to a separate file. I also want to smooth the measurements and do the same for the smoothed measurements.
This is my code:
%%Get measurements' matrix
measurements=cell2mat(data(:,2:5));
%%Split 'measurements' matrix based on flag in first column
A = arrayfun(@(x) measurements(measurements(:,4) == x, :),...
unique(measurements(:,4)),'uniformoutput', false);
%%Get the list of unique location names
loctn_names=unique(loctns);
%%Smooth measurements
% Save smoothed and original values to a separate file for each location
[rw,cw]=size(loctn_names);
count=0;
for i = 1:rw
values = A{i,:}(:,1); % access arrays in 'A' with content indexing (curly
% brackets) then access first column (values) with
% regular indexing (parentheses)
j=length(values); % access variable 'data' to create
stations=data(count+1:count+j,1); % a 1D array of station names
count=count+j; % to append to the output file
IN = A{i,1}(:,1:3); % creating matrix of data for each loctn
tempname=strcat(char(loctn_names(i)),'_X-Y-V.txt'); % temporary file name
save(tempname, 'IN', '-ASCII'); % save matrix of data to output file
%save(tempname, 'stations', '-append'); % append station names to file
valuesSM=conv(values,[0.5 1 0.5],'same')/2; % smoothing by convolution
valuesSM(1)=values(1);
valuesSM(end)=values(end); % ensuring extremes are same
% as in original values
OUT = IN; OUT(:,1)=valuesSM(:); % creating matrix of data for each loctn
tempname1=strcat(char(loctn_names(i)),'_X-Y-smooth_V.txt') % file name
save(tempname1, 'OUT', '-ASCII'); % save matrix of data to output file
%save(tempname1, 'stations', '-append'); % append stations names to file
end
It is all working as expected, except for the two lines to append the station names, which are commented out. If I uncomment them, I get this error message:
Error using save
Unable to write to MAT-file \\...\Measurements\AS-01_X-Y-V.txt
File may be corrupt.
Does the append option as described in here only apply to .mat files? If yes, in what other way can I append the variable to the output file?
Thank you.

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采纳的回答

James Tursa
James Tursa 2015-3-26
You still need to tell MATLAB that it is an ASCII text file you are writing to and not a mat file. E.g.,
save(tempname1, 'stations', '-append', '-ascii')
  2 个评论
Matteo Niccoli
Matteo Niccoli 2015-3-26
编辑：Matteo Niccoli 2015-3-26
HI James, thanks for your answer. if I do as you suggest, I do not get the error, but I do get a warning:
Warning: Attempt to write an unsupported data type to an ASCII file.
Variable 'stations' not written to file.
So I still do not get the desired result. Is it not possible to append strings? Any suggestions about this?
James Tursa
James Tursa 2015-3-26
编辑：James Tursa 2015-3-26
Yes, it appears save will convert your string to numeric and then write that out. You may have to resort to fwrite for this. E.g.,
fid = fopen(tempname1,'at'); open in append ASCII text mode
fwrite(fid,stations,'*uchar'); % append the string as character data
fprintf(fid,'\n'); % append a newline
fclose(fid); % close the file
Or you may need to wrap a loop around the fwrite and fprintf if stations is a cell array of strings and you want to print one string per line, etc.

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