dlmwrite with a header

Hello,

I am trying to write data to a file. I have no problem just writing the file but I want the header positions to match the columns

dlmwrite([savepath,'/myFile.txt'],[])  % save path is the path defined before I create an         %empty file first.
fid = fopen([savepath,'/myFile.txt'],'wt');
fprintf(fid, '%s\t %s\t %s\n', 'x','y1','y2');  % header
dlmwrite([savepath,'/myFile.txt'],MyData,'delimiter','\t','precision',['%10.',num2str(12),'f'],'-append');  % MyData is the file. 
fclose(fid);

I would appreciate it if you can point out my mistake.

Answer 1

[Walter Roberson]

You need to fclose(fid) before you dlmwrite() to the file. Also, you do not need to dlmwrite() it before you fopen() it.

filename = fullfile(savepath, 'myFile.txt');
fid = fopen(filename, 'wt');
fprintf(fid, '%s\t%s\t%s\n', 'x','y1','y2');  % header
fclose(fid);
dlmwrite(filename,MyData,'delimiter','\t','precision',['%10.',num2str(12),'f'],'-append');

[Sunny Lightman]

not work for me ... sorry

[Walter Roberson]

I made a minor correction.

[Turbulence Analysis]

Hi Walter,

Hi,

I need to insert below header file in the first row of the each txt file, please assist me in how to do this..

#DaVis 8.4.0 2D-vector 12 62 75 "position" "mm" "position" "mm" "velocity" "m/s"

I tried something like this, but didn't work.. Please help me with this....

for j =1:1:2
fileName = sprintf('test%d.txt',j);
fid = fopen(filename,'w');
fprintf(fid, 'HEADER 1 \n');
fclose(fid);
end
for k = 1:1:2
UFF = X_filter(1:ni*nk,k);
VFF = X_filter(1+ni*nk:2*ni*nk,k);
UFF1 =reshape (UFF,ni,nk)';
VFF1 =reshape (VFF,ni,nk)';
UUFFF1 = reshape (UFF1, 4650,1);
VVFFF1 = reshape (VFF1,4650,1);
xxx = reshape (X,4650,1);
yyy = reshape (Y,4650,1);
fileName = sprintf('test%d.txt',k);
dlmwrite(fileName,[xxx yyy UUFFF1 VVFFF1], 'delimiter','\t' );
end

[Walter Roberson]

I do not think it is profitable to fight with dlmwrite() for something like this.

for k =1:1:2
  fileName = sprintf('test%d.txt',k);
  fid = fopen(filename,'w');
  fprintf(fid, '%s\n', '#DaVis 8.4.0 2D-vector 12 62 75 "position" "mm" "position" "mm" "velocity" "m/s"');
  UFF = X_filter(1:ni*nk,k);
  VFF = X_filter(1+ni*nk:2*ni*nk,k);
  UFF1 = reshape (UFF,ni,nk)';
  VFF1 = reshape (VFF,ni,nk)';
  fprintf(fid, '%.17g\t%.17g\t%.17g\%.17g\n', [X(:) Y(:) UFF1(:) VFF1(:)].');  %transpose is important!
  fclose(fid);
end

You can adjust the %.17g as needed. %.17g should be enough that the values can be exactly reconstructed.

Question: are any of those variables complex-valued? Complex values need additional work. And your use of the conjugate transpose operator ' becomes questionable for complex values.

[Turbulence Analysis]

Many thanks for your reply. I did tried with this, Actually I supposed to get the values as arranged in test1.txt, however, I am getting different as shown in teest1.tx, as you see everything arranged in a row..

I modified bit, bcoz i need to have data arranged in 4650 rows and 4 columns in txt file..

for k =1:1:3
  fileName = sprintf('teest%d.txt',k);
  fid = fopen(fileName,'w');
  fprintf(fid, '%s\n', '#DaVis 8.4.0 2D-vector 12 62 75 "position" "mm" "position" "mm" "velocity" "m/s"');
  UFF = X_filter(1:ni*nk,k);
  VFF = X_filter(1+ni*nk:2*ni*nk,k);
  UFF1 = reshape (UFF,ni,nk)';
  VFF1 = reshape (VFF,ni,nk)';
  UUFFF1 = reshape (UFF1, 4650,1);
  VVFFF1 = reshape (VFF1,4650,1);
  xxx = reshape (X,4650,1);
  yyy = reshape (Y,4650,1);
  fprintf(fid, '%.17g\t%.17g\t%.17g\%.17g\n', [xxx(:) yyy(:) UUFFF1(:) VVFFF1(:)].');  %transpose is important!
  fclose(fid);
end

[Turbulence Analysis]

Hi, I solved the issue.. It's fine now..

[Walter Roberson]

What was the difficulty?

With the format you had, I do not see how you could have gotten the output you posted.

[Turbulence Analysis]

Hi, I did it in following way...

for k = 1:1:100
filename = sprintf('test%d.txt',k);
fid = fopen(filename,'w');
fprintf(fid, '#DaVis 8.4.0 2D-vector 8 92 112 "position" "mm" "position" "mm" "velocity" "m/s" \n');
fclose(fid);
end

for k = 1:1:100
UFF = X_filter(1:ni*nk,k);
VFF = X_filter(1+ni*nk:2*ni*nk,k);
UFF1 =reshape (UFF,ni,nk)';
VFF1 =reshape (VFF,ni,nk)';
UUFFF1 = reshape (UFF1, 10304,1);
VVFFF1 = reshape (VFF1,10304,1);
xxx = reshape (X,10304,1);
yyy = reshape (Y,10304,1);
fileName = sprintf('test%d.txt',k);
dlmwrite(fileName,[xxx yyy UUFFF1 VVFFF1],'delimiter','\t','-append');
end