File names in plots legend, from struct data; Matlab says is not an array.

I have multiple files with struct data, and I want to place a legend with a group of data.

I tried to use the Benjamin Kraus to solve it, but the message of Matlab is: Cell contents assignment to a non-cell array object.

https://www.mathworks.com/matlabcentral/answers/81979-an-elegant-alternative-to-nested-for-loops-for-plotting-simulations The code which I wrote:

for i = 1:numreg
    leg{i} = [BLR4.record{i}.name];
    C1 = BLR4.record{i}.T;
    C2 = BLR4.record{i}.Sd;
    plot (C1,C2)
    hold on
end
legend(leg)

[Stephen23]

[BLR4.record{i}.name]

If BLR4.record{i} is a scalar structure, then those square brackets are superfluous:

https://www.mathworks.com/matlabcentral/answers/35676-why-not-use-square-brackets

Note also that using a non-scalar structure might be better than a cell array of scalar structures:

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

Answer 1

[Stephen23]

Probably leg is not a cell array, so trying to use cell array indexing with it is going to be an error.

Solution: make leg a cell array:

leg = cell(1,numreg);
for ...
    leg{k} = ...
    ...
end

[Isai Fernandez]

Thanks you so much. The data in this file structure is in text form, I don't know if it is a problem. When I use your suggestion: Error using cell Size inputs must be scalar.

[Stephen23]

@Isai Fernandez: please upload your code by clicking the paperclip button. Also show us the complete error message. This means all of the red text.

[Isai Fernandez]

@Stephen Cobeldick

Here is my code.

[Stephen23]

I also asked for the complete error message. Here is that request again, in case you missed it:

Also show us the complete error message. This means all of the red text.

[Isai Fernandez]

@Stephen This is the message:

Error using cell  
Size inputs must be scalar.

Error in DynT3 (line 16)
leg = cell(1,numreg);

[Image Analyst]

Please look at this link first http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/

Then figure out why "numreg" is an array, cell, or table instead of a scalar (a single integer number).

whos numreg

If you want, you can come back here and tell us what the above line of code puts into the command window.

[Stephen23]

In your code you define numreg like this:

numreg = size(BLR4.record);

which means that numreg will be a numeric vector with atleast two elements (i.e. a vector). But to use cell (and colon reliably) you will need to use a scalar. Most likely you want the number of rows, so you can simply specify that you only want that single value (i.e. scalar) when you call size:

numreg = size(BLR4.record,1);

[Isai Fernandez]

@Stephen Cobeldick Yeah. Thank you so much, that was it.