error in calling a variable from another mat file

after doing some coding I have run a loop and saved values in cell R

for r=1:En
    R{r} =E(Ec+Ea(r,:),:);
end

I have saved a variable of cell in a matfile named

save('data_12x6','R')

where 'data_12x6' is fle name and 'R'is variable . now I want to call this variable in the below code

for r=1:numel(R)
    X=(R{r}*x).*y';
    XX(r)=(sum(X))*0.01; 
end

I an trying this

R=load('data_12x6','R')
for r=1:numel(R)
      X=(R{r}*x).*y';
      XX(r)=(sum(X))*0.01; 
  end

but it is giving an error that

Warning: Variable 'R' not found.
R = 

struct with no fields.

Cell contents reference from a
non-cell array object.

how can I do this?

[Jan]

While the code to create R does not matter here, the command for saving would be important. Please post this detail.

[Walter Roberson]

R=load('data_12x6','R')

would always give back a struct in that form of load(). There are forms of load() that return back values instead of a struct, but you cannot request particular variables when you use them.

The warning is telling you that it did not find a variable R inside data_12x6.mat

[Walter Roberson]

Please show the output of

whos -file data_12x6

Answer 1

[Jan]

R = rand;
save('data_12x6', 'R');

matfile('data_12x6')
>>  Properties:
>>    Properties.Source: 'D:\MFiles\data_12x6.mat'
>>  Properties.Writable: false                    
>>                    R: [1x1 double]

Q = load('data_12x6')
>> Q.R = 0.8651243

Q = load('data_12x6', 'R')
>> Q.R = 0.8651243

Q = load('data_12x6', 'Miss')
>> Warning: Variable 'Miss' not found. 
>> Q = 
>>   struct with no fields.

This means, that your data_12x6 file does not contain the variable R. This can happen only, if it was not created by |save('data_12x6', 'R'). I guess, that the current folder has changed. Prefer to use absolute path names:

folder = tempdir;  % Or where you want to store the files
save(fullfile(folder, 'data_12x6.mat'), 'R');
...
FileData = load(fullfile(folder, 'data_12x6.mat'));
R        = FileData.R;