format data into string and write a txt file

Hi,

I have the following cell,

a={[1E5 0 0 7.82E12 0]
 [-1 0 0 -1 0]};

and I want to write a text file with the following format

 1.0000000000000000E+05  0.0000000000000000E+00  0.0000000000000000E+00  7.8200000000000000E+12  0.0000000000000000E+00
-1.0000000000000000E+00  0.0000000000000000E+00  0.0000000000000000E+00 -1.0000000000000000E+00  0.0000000000000000E+00

As in two blank spaces at the beginning of the line if the first value is positive (line 1) and one blank space if it is negative (line 2), the "-" uses one space. There are also two blank spaces in between the values (if the value is negative the "-" uses one of those blank spaces).

First I tried converting a to a string cell:

for i=1:2
  a{i}=num2str(a{i},'%.16e');
end

And I get this:

a =

2×1 cell array

    {'1.0000000000000000e+050.0000000000000000e+000.0000000000000000e+007.8200000000000000e+120.0000000000000000e+00'     }
    {'-1.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00-1.0000000000000000e+00 0.0000000000000000e+00'}

There are no blank spaces at all. Is it possible to specify the number of blank spaces in between the values?

Thank you,

Answer 1

[Stephen23]

A cell array of numeric vectors is quite inconvenient to work with, so the first thing to do is convert it to a much easier to use numeric matrix:

a = {[1E5,0,0,7.82E12,0],[-1,0,0,-1,0]};
m = vertcat(a{:});

Method one: dlmwrite:

dlmwrite('sample.txt', m, 'delimiter',' ', 'precision','% .16E')

Method two: fprintf:

fmt = repmat(' % .16E',1,size(m,2));
fmt = [fmt(2:end),'\n'];
fprintf(fmt,m.')

prints this:

 1.0000000000000000E+005  0.0000000000000000E+000  0.0000000000000000E+000  7.8200000000000000E+012  0.0000000000000000E+000
-1.0000000000000000E+000  0.0000000000000000E+000  0.0000000000000000E+000 -1.0000000000000000E+000  0.0000000000000000E+000

To write to a text file, add fopen and fclose:

[fid,msg] = fopen('sample.txt','wt');
assert(fid>=3,msg)
fprintf(fid,fmt,m.')
fclose(fid)

[FM]

Thank you! Is there a way I can add one blank space at the beginning of each line in the text file? That is the only missing

[FM]

Oh I just modified fmt like this and it works!

fmt = [' ',fmt(2:end),'\n'];

[Stephen23]

"Is there a way I can add one blank space at the beginning of each line in the text file? That is the only missing"

Of course, that is easy (I removed it, because it is missing from your example data shown on this page. This is why it is always better to upload a sample file, rather than relying on the markup of this page, which can change displayed characters). Use these:

Method one:

'precision',' % .16E'

Method two:

fmt = [repmat(' % .16E',1,size(m,2)),'\n'];

Take another look at your proposed solution:

fmt = [' ',fmt(2:end),'\n'];

The fmt char vector's first character was a space character (as defined inside the repmat), so why remove that space character, just to add another space character?

Answer 2

[madhan ravi]

a={[1E5 0 0 7.82E12 0]
 [-1 0 0 -1 0]};

dlmwrite('sample.txt',a,'delimiter','\t','precision','%0.16e')

[madhan ravi]

Try the updated answer

[madhan ravi]

1.0000000000000000e+05  0.0000000000000000e+00  0.0000000000000000e+00  7.8200000000000000e+12  0.0000000000000000e+00
-1.0000000000000000e+00  0.0000000000000000e+00  0.0000000000000000e+00  -1.0000000000000000e+00  0.0000000000000000e+00

[madhan ravi]

the above is the format in the text file

[FM]

Hi,

When I try what you suggest I do get a blank space between the values but it writes down both rows of a in the same line in the text file. Also, is there a way to have 2 blank spaces in between the values, not just one?

Thanks for your help!

[madhan ravi]

_it writes down both rows of a in the same line in the text file_

no there are two rows in my text file

[madhan ravi]

 _I try what you suggest I do get a blank space between the values_

thats how you can distinguish the values right??

[madhan ravi]

see attached file

[FM]

I copied pasted but you wrote and it gives me a text file with only one line of text, I changed the file extension .txt to .asc (which is ultimately the file extension I need) and now it works, I have two lines of text, thanks!

_thats how you can distinguish the values right??_

yes but the file I am writing is to be read by another software and unless I respect a specific format the other software is unable to read the file. That's why I need two blank spaces in between the values