Converting string to integer - indexing and multiple trials

I have 120 trials in one Matlab file, all trials are separate within the file and look similar to that of trial1.mat (attached). I am importing this Matlab file into Python and indexing into the correct spot with

cue_times = trial(['BehavioralCodes']['CodeTimes'], dtype=int)

**I know this is not a Python platform, and that is not my question, I am merely explaining what I'm doing when I get the error I am getting.**

I get the error that the list indices must be integers or slices, not str

I need to convert 'CodeTimes' within 'BehavioralCodes' in each trial (each trial is saved individually like trial1) from a string to an integer.

I have tried:

code_times = str2num('CodeTimes') but that gives me an empty array so I am definitely doing something wrong.

I am not sure how to index into the correct space and then to include all trials (perhaps a for loop?). Any help would be greatly appreciated!

Answer 1

[Askic V]

If you look into your data in Matlab, you will see that CodeTimes is actually an array of doubles and not strings:

cc = load (websave('trial1.mat', 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/1315225/trial1.mat'));

code_times = cc.Trial1.BehavioralCodes.CodeTimes;
code_numbers = cc.Trial1.BehavioralCodes.CodeNumbers;
vpa(code_times(1:5),6) % show first 5 elements

ans = 

code_numbers (1:5)

ans = 5×1

9 20 24 30 34

% check type
class(code_times)

ans = 'double'

class(code_numbers)

ans = 'double'

In Matlab you can use function round to round to the neareast integer:

code_times_int = round(code_times);
code_numbers_int = round(code_numbers);
% show first 5 elements
code_times_int(1:5)

ans = 5×1

7 750 862 923 3889

code_numbers_int(1:5)

ans = 5×1

9 20 24 30 34

If round is not what you want, then check

help floor

 FLOOR  Round towards minus infinity.
    FLOOR(X) rounds the elements of X to the nearest integers
    towards minus infinity.
 
    See also ROUND, CEIL, FIX.

    Documentation for floor
       doc floor

    Other uses of floor

       codistributed/floor    duration/floor    sym/floor
       datetime/floor         gpuArray/floor    tall/floor
       dlarray/floor          matlab/floor

help ceil

 CEIL   Round towards plus infinity.
    CEIL(X) rounds the elements of X to the nearest integers
    towards infinity.
 
    See also FLOOR, ROUND, FIX.

    Documentation for ceil
       doc ceil

    Other uses of ceil

       codistributed/ceil    dlarray/ceil     gpuArray/ceil    sym/ceil
       datetime/ceil         duration/ceil    matlab/ceil      tall/ceil

[Antoinette Burger]

Thank you, @Askic V! How would I include all 120 trials without doing each one individually (rounding the nearest integer)?

Also, is there a specific way of indexing into all the variables (trials) to get to CodeTimes, as it is embedded in BehavioralCodes (I saw what you did for Trial1 above, but to include all the trials I am a bit lost still)?

[Askic V]

This loop will give you an answer (assuimg the name is trialX.mat)

for i = 1:120 % assuming 120 files in total
    filename = ['trial', num2str(i), '.mat']; % form filename
    % load filename and perform processing like already described
    fprintf('%s\n',filename)
end

trial1.mat
trial2.mat
trial3.mat
trial4.mat
trial5.mat
trial6.mat
trial7.mat
trial8.mat
trial9.mat
trial10.mat
trial11.mat
trial12.mat
trial13.mat
trial14.mat
trial15.mat
trial16.mat
trial17.mat
trial18.mat
trial19.mat
trial20.mat
trial21.mat
trial22.mat
trial23.mat
trial24.mat
trial25.mat
trial26.mat
trial27.mat
trial28.mat
trial29.mat
trial30.mat
trial31.mat
trial32.mat
trial33.mat
trial34.mat
trial35.mat
trial36.mat
trial37.mat
trial38.mat
trial39.mat
trial40.mat
trial41.mat
trial42.mat
trial43.mat
trial44.mat
trial45.mat
trial46.mat
trial47.mat
trial48.mat
trial49.mat
trial50.mat
trial51.mat
trial52.mat
trial53.mat
trial54.mat
trial55.mat
trial56.mat
trial57.mat
trial58.mat
trial59.mat
trial60.mat
trial61.mat
trial62.mat
trial63.mat
trial64.mat
trial65.mat
trial66.mat
trial67.mat
trial68.mat
trial69.mat
trial70.mat
trial71.mat
trial72.mat
trial73.mat
trial74.mat
trial75.mat
trial76.mat
trial77.mat
trial78.mat
trial79.mat
trial80.mat
trial81.mat
trial82.mat
trial83.mat
trial84.mat
trial85.mat
trial86.mat
trial87.mat
trial88.mat
trial89.mat
trial90.mat
trial91.mat
trial92.mat
trial93.mat
trial94.mat
trial95.mat
trial96.mat
trial97.mat
trial98.mat
trial99.mat
trial100.mat
trial101.mat
trial102.mat
trial103.mat
trial104.mat
trial105.mat
trial106.mat
trial107.mat
trial108.mat
trial109.mat
trial110.mat
trial111.mat
trial112.mat
trial113.mat
trial114.mat
trial115.mat
trial116.mat
trial117.mat
trial118.mat
trial119.mat
trial120.mat

[Antoinette Burger]

Thank you @Askic V!!