how to convert cell array of struct to matrix

Hey,

I have cell array, each contain struct.

data{1}.time=[1:10]

data{1}.pos=[1:10]

data{2}.time=[5:100]

data{2}.pos=[1:96]

i would like to create a time matrix and a pos matrix.

the matrix can be sparse or filled with nan where the size do not match tha max length of the time/pos vector.

so far i was using:

for n=1:2

time(1:length(data{n}.time),n)=data{n}.time

end

thanks

[Stephen23]

Note that square brackets are a concatenation operator, and are superfluous in this code: [1:10] because the colon operator already returns a vector, which you then concatenate with ... nothing. Get rid of the brackets, they literally do nothing**.

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

** except mislead experienced MATLAB users who know that they are a concatenation operator, and mislead beginners who believe that they are some kind of required "list" operator (which MATLAB does not have).

[ORR]

thanks

Answer 1

[Stephen23]

Rather than creating a cell array of scalar structures, you should create one single structure array:

>> S(1).time = 1:10; % I also removed the superfluous square brackets
>> S(1).pos  = 1:10;
>> S(2).time = 5:100;
>> S(2).pos  = 1:96;

Then you can trivially process all of the field data with one simple comma-separated list, e.g.:

>> Vtime = [S.time];
>> Vpos  = [S.pos];

And you can use this to easily create the required matrix by downloading Jos's excellent padcat:

>> Mtime = padcat(S.time);
>> Mpos  = padcat(S.pos);

Read more about comma-separated lists:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

Note that you can also use a comma-separated list to convert your cell array of scalar structures to a much better structure array:

S = [data{:}];

(this requires that all of the structures have the same fields)

[ORR]

thanks but you created S as a 1X2 struct.

while my data is 1X2 cell. each cell contain the struct. this is how the data recieved.

[Stephen23]

"...while my data is 1X2 cell. each cell contain the struct."

Which is why at the end of my answer I showed how you can convert the cell array of structures to one structure array.

Did you try it?

Don't worry, that conversion will be quite efficient because it does not copy your data arrays, just creates a small list of references to them in memory.

[ORR]

yes.

dimentions of matrix being concatenated are not consistent