labelling chunks of data consecutively - matlab

Question

I have data contained in 4195X1 double called z1. I would like to extract data in 120 chunks and label them z1_1_120, z1_120_240, z1_240_360, etc using matlab. I would like to both extract them and also label them in this manner in a loop. Here's what I've done so far, but am unsure as to how to proceed:
load(z1)
for i = 1:4195
q=z1(i);
q1(i,:)=q;
q2=q1(1:120:end);
end
z1=q2(1:end);

Answer 1

As Daniel commented, don't do it!
In case you want the kind of labeling you described, you may either use a Table or a Struct data types.
Read the following post:
The solution is easy: Don't do this. It is a shot in your knee
The following solution creates a Table and a Struct.
The Table needs some padding, because all columns must be the same length (and 4195 is not a multiple of 120).
The code is a bit complicated, I tried to solve it without using for loops (for making the solution more efficient [and more interesting]).
I hope you mange to follow the code, and learn from it...
Here is a code sample (explanations are in the comments):
% Fill z1 with sequential numbers (just for testing)
z1 = (1:4195)';
z1_len = length(z1);
% Compute length remainder from 120
len_mod120 = mod(z1_len, 120);
pad_len = mod(120 - len_mod120, 120);
% If length of z1 is not a multiple of 120, add zeros padding at the end.
pad_z1 = padarray(z1, pad_len, 0, 'post'); % After padding, length of z1 is 4120
% Reshape pad_z1 into a matrix where each row is 120 elements
% Z1(:, 1) gets z1(1:120), Z1(:, 2) gets z1(121:240)...
Z1 = reshape(pad_z1, [], length(pad_z1)/120);
% Build naming indices
name_idx = zeros(1, 2*length(pad_z1)/120);
name_idx(1:2:end) = 1:120:length(pad_z1); %First naming index: 1 121 241 361 ...
name_idx(2:2:end) = name_idx(1:2:end) + 120-1; %Second naming index: 120 240 360 480
% String of elements names separated by space
str_names = sprintf('z1_%d_%d ', name_idx); % 'z1_1_120 z1_121_240 z1_241_360 z1_361_480 ...
% Build cell array of names
var_names = split(str_names(1:end-1)); %{'z1_1_120'}, {'z1_121_240'}, {'z1_121_240'}
% Build table, where each column is 120 elements, and column names are 'z1_1_120' 'z1_121_240' 'z1_121_240'
% A table is useful, if you don't care about the zero padding we added at the beginning
% https://www.mathworks.com/matlabcentral/answers/376985-how-to-convert-string-to-variable-name
T = array2table(Z1, 'VariableNames', var_names);
% Convert table to struct:
% S.z1_1_120 holds first 120 elements, S.z1_121_240 holds next 120 elements...
S = table2struct(T, 'ToScalar', true);
% Fix the last field in the stract - should contain only 115 elements (not 120)
S = rmfield(S, var_names{end}); % Remove the last field from the struct
% last_field_name = 'z1_4081_4195'
last_field_name = sprintf('z1_%d_%d', name_idx(end-1), z1_len);
% Add the last field (only 195 elemtns)
S.(last_field_name) = z1(end-len_mod120+1:end);
Table T:
T =
120×35 table
z1_1_120 z1_121_240 z1_241_360 z1_361_480 ...
________ __________ __________ __________
1 121 241 361
2 122 242 362
3 123 243 363
4 124 244 364
5 125 245 365
6 126 246 366
... ... ... ...
Example for accessing the first element: T.z1_1_120(1)
Struct S:
S =
struct with fields:
z1_1_120: [120×1 double]
z1_121_240: [120×1 double]
z1_241_360: [120×1 double]
z1_361_480: [120×1 double]
z1_481_600: [120×1 double]
z1_601_720: [120×1 double]
z1_721_840: [120×1 double]
...
z1_4081_4195: [115×1 double]
Example for accessing the first element: S.z1_1_120(1)