algorithm - Need Help in Contour Plot in Matlab -

i trying plot contour of shifted schwefel problem function keep having error: z must size 2x2 or greater. have searched on forum , information have helped little, not fix above error. information got forum lead me trying code:

min = -50; max = 50; steps = 20; c = linspace(min, max, steps); % create mesh [x, y] = meshgrid(c, c); % create grid %o=-50+100*rand(1,2); %c = c - repmat(o,1,10);  i=1:length(x)     j=1:length(y)     o=-50+100*rand(1,2);     x=x-repmat(o,20,10);     f = max(abs(x), [], 2);      end end  figure, contour(x,y,f);  figure, surfc(x, y,f); 

now have error z, the value of f atleast 2x2 or greater. know f taking 1 input , therefore output one. tried having in nested loops, still giving me array of vectors not matrix of atleast 2x2. if input two, problem fine, problem is, 1 input. know how can make "f" output matrix of atleast 2x2 can plot z of contour?

there few things note:

1.) jacob robbins pointed out correctly in comment, should avoid using names matlab functions variable names (in case min , max). 1 easy way this, use upper case letters variable names.

2.) correct in saying fis 1 output (though one output in case not single number, vector). is, because don't assign indexing within loop.

3.) yes, both contour , surfc need @ least 2x2 - because plot information on grid, @ least 2x2 in nature.

4.) in particular case, 2 loops may not necessary. seem manipulating x-vector , grid regular. hence might want try loop:

for i=1:length(x)     o=-50+100*rand(1,2);     x=x-repmat(o,20,10);     f(:,i) = max(abs(x), [], 2); end 

now, f of size 20x20, corresponds x- , y-grid. also, contour , surfc command produce plots.

5.) 1 last comment: output of function , results of web-search "shifted schwefel function" different. question if implementation of shifted schwefel function correct, should asked new question.