How to sorting categorical array for plotting

Hi everyone,

I have categorical array that use to plot. But in the plot, the x-axis isn't numerically. Its plot from M1, M10, M2, M3...M9 instead M1,M2,...M10

male=MakeMaleSample(10);
male=categorical(male);

data_male=[1:10];
plot(male,data_male);
grid on

function male=MakeMaleSample(n)
male="M"+string(1:n);
end

Thanks for your help

Answer 1

[Stephen23]

By default the categories are sorted into character order, not alphanumeric order.

S = "M"+(1:10);
A = categorical(S)

A = 1×10 categorical array
     M1      M2      M3      M4      M5      M6      M7      M8      M9      M10 

C = categories(A) % default order = sorted by character.

C = 10×1 cell array
    {'M1' }
    {'M10'}
    {'M2' }
    {'M3' }
    {'M4' }
    {'M5' }
    {'M6' }
    {'M7' }
    {'M8' }
    {'M9' }

Y = 1:10;
plot(A,Y);

Solution one: You can specify the order when creating the categorical array:

D = categorical(S, "M"+(1:10)) % looks the same as A ...

D = 1×10 categorical array
     M1      M2      M3      M4      M5      M6      M7      M8      M9      M10 

categories(D) % but the categories are in the expected order.

ans = 10×1 cell array
    {'M1' }
    {'M2' }
    {'M3' }
    {'M4' }
    {'M5' }
    {'M6' }
    {'M7' }
    {'M8' }
    {'M9' }
    {'M10'}

Solution two: change the category order of an existing categorical array using REORDERCATS, e.g.:

[~,X] = sort(str2double(replace(C,"M","")));
B = reordercats(A,C(X));
categories(B)

ans = 10×1 cell array
    {'M1' }
    {'M2' }
    {'M3' }
    {'M4' }
    {'M5' }
    {'M6' }
    {'M7' }
    {'M8' }
    {'M9' }
    {'M10'}

Solution three: For compactness you could also use NATSORT (must be downloaded here):

E = reordercats(A,natsort(categories(A)));
categories(E)

ans = 10×1 cell array
    {'M1' }
    {'M2' }
    {'M3' }
    {'M4' }
    {'M5' }
    {'M6' }
    {'M7' }
    {'M8' }
    {'M9' }
    {'M10'}

Once you have the categories in the required order, then your plot will look as you expect:

plot(E,Y);

[Moh Rifqy Risqullah]

Thank you

This is the complete answer

Answer 2

[dpb]

function male=MakeMaleSample(n)
  male=categorical("M"+1:n,"M"+1:n);
end

To force a non-lexical sort order, you have to specify the specific order explicitly...

[Moh Rifqy Risqullah]

Thank you

This is the simple answer