creating matrix from for loop with system command output

Hi All,

I would greatly appreciate some help on this.

I am trying to do the following.

Within a for loop, run 2 system commands and have the ouputs from those two commands make up all three elements of one row of a matrix for each iteration of the loop. I would then like to print the entire matrix to an excel file.

I tried this:

   for i=1:3,

    command1 = ['fslmeants -i image1 -m example_' num2str(i) '.nii.gz' ]

    C(i,1) = evalc('system([command1])')

    command2 = ['fslstats example_' num2str(i) ' -V']

    C(i,2:3) = evalc('system ([command2])')

   end

I received the following error message:

??? Assignment has more non-singleton rhs dimensions than non-singleton subscripts

Error in ==> name_of_script at 8 C(i,1) = evalc('system ([command1])')

I then tried this

for i=1:3,

   command1 = ['fslmeants -i image1 -m example_' num2str(i) '.nii.gz' ]

    A = evalc('system([command1])')

    command2 = ['fslstats example_' num2str(i) ' -V']

    B = evalc('system ([command2)')

   end

the output for system ([command1]) when I don't try to assign a matrix element to it is

A =

0.302714 ans =

     0

the output for system ([command2]) when I don't try to assign matrix elements to it is

B =

1413 19506.814453

ans =

     0

If I then type B(1,2) I get

ans =

4

which gives me the second digit of the first number in B, not the second number (19506.814453) as I wanted.

I then checked if B was a character array as follows:

   ischar B

   ans =

       1

So I guess if I can find a way for matlab to recognise the output of system([command1]) and system ([command2]) as 3 elements of the same row for each iteration of the for loop I'd be sorted.

So ideally, the first row of the Matrix C would be

C(1,:) = 0.302714 1413 19506.814453

and an extra row would be added with each iteration of the for loop.

Can anyone enlighten a lost soul?

All help much appreciated,

Best wishes,

Sean

Answer 1

[Walter Roberson]

B = evalc('system([command2])');
B = regexp(B,' +','split');

B{2} will now be the second column.