Using nested for-loop to generate a table of numbers - matlab

Question

I try to write a function in which print this output:
1
2 4
3 6 9
4 8 12 16
5 10 15 20 25
I wrote this code, but I'm not getting the desired output:
rows = 5;
% there are 5 rows
for i=1:rows
for j=1:i
b=i*j;
end
fprintf('%d\n',b)
end
How to I need to correct this algorithm or can you tell me, if there are any other alternate methods to solve this?

Answer 1

I don't know what you mean by "print", but this is how you could start:
%// initial vector
a = 1:5;
A = tril( bsxfun(#plus,a(:)*[0:numel(a)-1],a(:)) )
%// or
A = tril(a.'*a) %'// thanks to Daniel!
mask = A == 0
out = num2cell( A );
out(mask) = {[]}
A =
1 0 0 0 0
2 4 0 0 0
3 6 9 0 0
4 8 12 16 0
5 10 15 20 25
out =
[1] [] [] [] []
[2] [ 4] [] [] []
[3] [ 6] [ 9] [] []
[4] [ 8] [12] [16] []
[5] [10] [15] [20] [25]
To print it to a file, you can use.
out = out.'; %'
fid = fopen('output.txt','w')
fprintf(fid,[repmat('%d \t',1,n) '\r\n'],out{:})
fclose(fid)
and you get:
just for the command window:
out = out.'; %'
fprintf([repmat('%d \t',1,n) '\r\n'],out{:})
will be sufficient. Choose your desired delimiter, if you don't like '\t'.
If you insist on a nested for loop, you can do it like this:
rows = 5;
% there are 5 rows
for ii = 1:rows
for jj = 1:ii
b = ii*jj;
if ii <= jj
fprintf('%d \n',b)
else
fprintf('%d ',b)
end
end
end
displays:
1
2 4
3 6 9
4 8 12 16
5 10 15 20 25