Storing Arrays in a Matrix

Hi, I'm currently trying to make a function that outputs an array containing all the different arrays for a stage of separations:

function stage_out = calc_stage(frac, ratio, Pin, Pout, perm, flux, total)
    stage_k = calc_K(frac, flux, Pin, Pout);
    stage_rej = calc_rej(frac, ratio, stage_k);
    stage_perm = calc_perm(stage_rej, stage_k);
    flow_perm = total*ratio;
    flow_rej = total-flow_perm;
    stage_perm_flow = stage_perm*flow_perm;
    stage_rej_flow = stage_rej*flow_rej;
    stage_out = [stage_k; stage_rej; stage_perm; stage_rej_flow; stage_perm_flow];
end

Stage_k ... etc are all 5x1 arrays, however when I call this function it outputs a single column array with a mixture of numbers in it. Coming over from Python, I'm not quite sure how this would work. How would I get this code to work as intended?

Thanks,

Edo

Edit: I fixed this issue, obviously changing the semicolons to colons helped. I was also using the wrong variable somewhere so this was also causing issues! Sorry for the bother.

Answer 1

[Paul]

Hi Edoardo,

The ; concatenates the elements vertically. Use a , to concatenate horizontally

x = (1:3).'; y = (4:6).';  % example 3 x 1 vectors
[x;y]

ans = 6×1

1 2 3 4 5 6

[x,y]

ans = 3×2

1 4 2 5 3 6

[Edoardo Modestini]

Hi, is there any way to have the arrays stored as arrays, eg if i called [x,y](1) it would display [1,2,3]?

[Stephen23]

See also the section "Matrices and Arrays" here:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

"is there any way to have the arrays stored as arrays, eg if i called [x,y](1) it would display [1,2,3]?"

In MATLAB nearly everything is an array, as the documentation explains:

https://www.mathworks.com/help/matlab/matlab_prog/fundamental-matlab-classes.html

Numeric arrays contain numeric values stored in contiguous memory. Python itself does not have anything like that (for contiguous numeric arrays you have to use numpy or some other extension). In contrast, the closest equivalent to Python's container types list and tuple is a cell array:

https://www.mathworks.com/help/matlab/cell-arrays.html

So if you really want to nest lots of separate vectors in a container array just like poor old Python, then by all means use a cell array. However writing MATLAB code as if it were Python is very unlikely to deliver good code, as you will miss out on the benefits of working with contiguous numeric data, e.g.:

https://www.mathworks.com/help/matlab/matlab_prog/vectorization.html

MATLAB is not Python.