matrix issue with null
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Hello, i have this code in mathematica and i want to do it in matlab:
T = Table[{Null, Null}, {Maxstep}]
t = Table[Null, {Maxstep}]
T2 = Table[{0, 0}, {Maxstep}]
How can i do it?(the null?) Thanks!
EDIT---->> Also,this : ml = Table[If[RandomReal[] < 0.5, 1, -1], {L}, {L}];
I tried this: ml=rand(L,L); if rand()<0.5 ml(:,:)==1 else ml(:,:)==-1 end ml
but it gives me random numbers 0-1 and i want only 1 and -1
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Accepted Answer
Matt Tearle
on 19 Feb 2011
If you want a 2-by-|Maxstep| table of nulls, you can do
T = NaN(2,Maxstep);
This way, T will be numeric. Otherwise, go with Matt Fig's suggestion of a cell array of empty arrays.
7 Comments
Matt Tearle
on 20 Feb 2011
If you want the sum of everything, you can reshape into a 1-D array. A neat short-cut syntax for this is sum(matrix(:))
More Answers (2)
Matt Tearle
on 19 Feb 2011
Best practice is to make separate posts for separate questions. For the first question, can you explain what the desired output is? (I haven't used Mma in ages)
For the second question, your approach wasn't bad, but your if condition invoked rand a second time, then set all of ml to 1 or -1. Try rounding, in conjunction with shifting and scaling:
ml = 2*round(rand(L,L)) - 1;
Matt Fig
on 19 Feb 2011
Since I don't have Mathematica, and many may not, can you show what the output of those commands is? That way we could try to match it in MATLAB. My best guess is you want something like this:
T = cell(1,Maxstep);
ml = rand(L,L);
ml(ml>.5) = 1;
ml(ml<=.5) = -1
Or all at once:
ml = round(rand(L,L))*2-1
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