If a structure exists in a file

I load several *.MAT files using a for loop, store the structures that I need, and get rid of the file. Each file contains several structures and I am only intersted in some of them. The code I use is below:

for i=[120:131 133:140 144:153]
    i
FileName=strcat(['DATA_' num2str(i) '.mat']);
load(FileName)

Bot{i}=(((cDA_Bottom_Speed.DATA.*1000)-4)/0.2133.*3.6/1.608)';
Mid{i}=(((cDA_Middle_Speed.DATA.*1000)-4)/0.2133.*3.6/1.608)';
Top{i}=(((cDA_Top_Speed.DATA.*1000)-4)/0.2133.*3.6/1.608)';
Ex{i}=(((cDA_External_Speed.DATA.*1000)-4)/0.2133.*3.6/1.608)';

end

In some files, the struture "cDA_External_Speed" doesnt exist. How can I check if it exists, I assign that to a cell ("Ex{i})". I am thinking a condition to use above

Ex{i}=(((cDA_External_Speed.DATA.*1000)-4)/0.2133.*3.6/1.608)';

The image shows the variables I have after importaning the file.

Thanks for your help

Answer 1

[Bjorn Gustavsson]

You can explicitly check for the existense of a variable in a .mat-file:

qwe = whos('-file','your-filename.mat','cDA_External_Speed')

if that variable doesn't exist whos will return an empty array, otherwise you'll get a struct with contenst something like this:

qwe =

  struct with fields:

          name: 'Tr'
          size: [125 1]
         bytes: 1000
         class: 'double'
        global: 0
        sparse: 0
       complex: 0
       nesting: [1×1 struct]
    persistent: 0

HTH