Split a matrix into a two submatrixes by a condition

Let "ex3" a matrix with an arbitrary length, which first column is gender (binary 0 or 1 for male o female), the second is age, the third is wage. How can I split this matrix into two submatrixes by gender using "for" and "if" functions? After that, i have to plot the wage versus the age, using plus sign (+) as a marker style for women and a circle (O) for men.

Anybody can give me an answer? I suppose that are few lines of code.

For the first part I've tried this:

for i=1:11
if ex3(i,1)==0
A=ex3(i,:)
else
B=ex3(i,:)
end
end

but this doesn't return me 2 matrixes, but a series of vectors.

[Iain]

Is there a reason you're restricting yourself to if and for?

[Gino Franco]

For learning reasons imposed by our teacher

Answer 1

[Mohammad Abouali]

If this is MATLAB programming class tell your teacher that using "for" and "if" is not necessary the correct way of learning matlab. Matlab has its own style of coding it's better to think that way. If it is a general programming class then the story is different.

So first the bad style MATLAB programming

female_ex3=[];
male_ex3=[];
for i=1:size(ex3,1)
  if (ex3(i,1))==0)
    male_ex3=[male_ex3;ex3(i,2:end)]; % Stripping of first column which tell you gender
  else
    female_ex3=[female_ex3;ex3(i,2:end)];
  end
end

now a more accepted style in MATLAB

    male_ex3=ex3( ex3(:,1)==0 , 2:end );
  female_ex3=ex3( ex3(:,1)==1 , 2:end );

NOTE that I assumed 0 means male and 1 means female.

[Gino Franco]

thank you

Answer 2

[Iain]

This is the "simple" answer:

 male = ex3(find(ex3(:,1) == 1),:);
 female = ex3(find(ex3(:,1) == 0),:);

[Mohammad Abouali]

You don't even need find . Look at the two last line of code in my answer.