save variables to a mat file by reading variable names from another mat file

Question

I have a mat file called names.mat. It has variables say var1="loop_no", var2="phase", var3="flow". These variables are already present in the base workspace. now i want to use this mat file to save similarly names variables in another mat file. i.e instead of writing variable names in the command save(filename,"var1","var2","var3") I want to be able to write the mat file names.mat somewhere in the command so that these variables are automatically saved in the file results.mat. Is it possible?

il_raffa il_raffa · Accepted Answer · 2017-06-23T09:25:06

You can exploit the dynamic field naming of the struct data type.

You can load the .mat file holding the list of variable in a struct by using load
then you can extract the names of the variables using the fieldnames function
then in a forloop you can create a cellarray holding the value of the variables read from the mat file (which are the names of the variables in theWorkspace you want to save)
the last step is to save this list of varaibles with the functnio save

A possible implementatin couls be:

% Define the variables holding the variable names
var1='loop_no'
var2='phase'
var3='flow'
% Save in a ".mat" file
save names.mat var1 var2 var3
% Create the variables in the Workspace
loop_no=100
phase=333
flow=123.456
% Load the file with the varaible names
tmp_var=load('names.mat')
% Get the names of the variables to be saved
var_names=fieldnames(tmp_var)
% Create a cellarray with the variables names
for i=1:length(fieldnames(tmp_var))
   var_list{i}=tmp_var.(var_names{i})
end
% Save the Workspace variables in a ".mat" file
save('new_mat_file.mat',var_list{:})

A test:

clear loop_no phase flow
load new_mat_file.mat
whos

  Name         Size            Bytes  Class     Attributes

  flow         1x1                 8  double              
  loop_no      1x1                 8  double              
  phase        1x1                 8  double    

[loop_no;phase;flow]

ans =

  100.0000
  333.0000
  123.4560

Hope this helps,

Qapla'

save variables to a mat file by reading variable names from another mat file

1 Answers