Undefined operator '+' for input arguments of type 'struct'.

Hi, I have been trying to run a script and got the error:

Undefined operator '+' for input arguments of type 'struct'.  

Error in coarsegrain (line 41)   sum = sum + y(scale*i + j);  

Error in mse (line 35)   scaled = coarsegrain(method,y,scale);

Displayed in the work space:   maxScale=3,

val 3x1280 double,

x 1x1 struct.

[Walter Roberson]

Duplicates https://www.mathworks.com/matlabcentral/answers/341103-hi-i-have-been-trying-to-run-a-script-and-got-the-error-undefined-operator-for-input-arguments