How can I make multiple max in elegant way?

Hello all, let's assume I have 8 vectors x1,x2,x3,...,x8 I can use: max(max(max(x1,x2),x3),x4) and so on... But how can I do it in a more elegant way?

Thanks in Advance

Answer 1

[Ced]

you could do

max(max([ x1 x2 x3 x4 x5 .... ]))

Since the first max is evaluated along the columns, I think it should be fast enough. Alternatively, you could of course do X = [ x1 x2 x3 ... ] and then max(X(:)). That's shorter, but depending on the length of your vectors, I would go with the first option. A common alternative is to use sort, e.g.

X_sorted = sort([ x1 x2 ... ]);
xmax = max(X_sorted(end,:))

but since for max, you don't need the matrix to be fully sorted, I would guess that max is actually faster.

[Eli Borodach]

Thanks you very much!

[Walter Roberson]

Are you looking for the overall maximum among the 8 vectors? Or are you looking for the maximum for each entry in the vector -- e.g.,

[max([x1(1), x2(1), x3(1), x4(1), x5(1), x6(1), x7(1), x8(1)]),
 max([x1(2), x2(2), x3(2), x4(2), x5(2), x6(2), x7(2), x8(2)]),
 ...
 max([x1(end), x2(end), x3(end), x4(end), x5(end), x6(end), x7(end), x8(end)]) ];

Your max(max(max(...max(x1,x2), x3), x4 ... code is taking maximum for each entry, which is what I coded for. Some of the solutions Ced posted are for the overall maximum.

Answer 2

[Walter Roberson]

If they have the same orientation but the orientation is not known ahead of time,

max( cat(3, x1, x2, x3, x4, x5, x6, x7, x8), [], 3)

The result would have the same orientation.

Or you could use

max( [x1(:), x2(:), x3(:), x4(:), x5(:), x6(:), x7(:), x8(:)], [], 2)

the result would be a column vector.

If you know that they are column vectors already you can leave out the (:)

[Eli Borodach]

Thank you very much!