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Hi, Does anyone know how i can plot contour of this function?

Here is what i tried but it did not work.

Any idea how i could solve this. Does any one know how to plot contour of functions which takes in one value like the above. Any time i try to plot the above function, it tells me that z must be atleast a 2x2. But i am taking in only one input and giving out a vector, how can it give out a matrix of atleast 2x2 inorder to plot the contour?

Here is what i tried but it did not work.

```
x = -50 + 100.*rand(50,2);
function f = func(x)
D = 2;
[ps, D] = size(x);
o=-50+100*rand(1,D);
x=x-repmat(o,ps,1);
f = max(abs(x), [], 2);
end
This is how i tried doing it:
cmin = -50;
cmax = 50;
steps = 20;
c = linspace(cmin, cmax, steps); % Create the mesh
[X1, X2] = meshgrid(c, c)
contour(X1,X2,f);
```

Any idea how i could solve this. Does any one know how to plot contour of functions which takes in one value like the above. Any time i try to plot the above function, it tells me that z must be atleast a 2x2. But i am taking in only one input and giving out a vector, how can it give out a matrix of atleast 2x2 inorder to plot the contour?

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Elevation above sea level as a function of longitude and latitude is one example.

What is your two dimensional map?

What are the units of your equal value lines?

Contours are usually associated with continuous functions?

What is the rand() function for?

At a more basic level, what are you hoping to accomplish?

```
x = -50 + 100.*rand(50,2);
```

This random matrix is going to be passed to the function func like this:```
eva = func(x)
```

The function returns an array for vectors which are 50 x 1. I try to plot contour of the resulting eva by doing This: My 2 dimensional map is This [X1, X2] = meshgrid(c, c) as it is shown here:```
cmin = -50;
cmax = 50;
steps = 20;
c = linspace(cmin, cmax, steps); % Create the mesh
[X1, X2] = meshgrid(c, c)
contour(X1,X2,eva);
```

The unite of my equal value line is:
```
steps = 20;
```

But any time i run this, it tell me that eva, has to be a matrix of atleast 2x2. As it is now it just give a matrix of 50 x 1. I need eva to be atleast 2x2 matrix so that i can plot the contour. I am now seeking for advice how to do this. Is there a way i can plot the contour? Any suggestion?
If you want to draw contours at 10 foot intervals, you interpolate along the edges to find all the interval values and then connect the points.

I have attached an example for a simple 2x2 matrix that represents one small map element.

I don't know what contours on a 1-D array could possibly mean.

Could you make a drawing showing the sort of plot you would like to see?

Contour-Plot-for-ExEx.pdf

SampleSchwefel.jpg

But at 21x21, there would be 441 data values representing the z-axis value/height of the function at

x = -100, -9-, -80, ...0, 10, 20, ... 100 and y = -100, -9-, -80, ...0, 10, 20, ... 100

In your example, the contour plot is the flat 2D plot at z=-460, not the colorful squarish cone that rises over it.

There are no random variables in your example.

Your first step should probably be to make a 2D matrix that samples your function at discrete points. Once you have a function, you can think about ways to plot it.

And I still don't know what you are trying to do or why you are trying to do it.

Are you really trying to do something with Genetic Algorithms and the Schwefel function?

```
M = 50;
n = 2;
x = -50 + 100.*rand(M,n);
cmin = -M;
cmax = M;
ngrid = 5.05;
x = cmin:ngrid:cmax;
y = cmin:ngrid:cmax;
o = -50+100*rand(1,n);
y = y - repmat(o,1,10);
x = x - repmat(o,1,10);
f = arrayfun(@tteee1,x);
figure;
contour(x,y,f);
figure;
surfc(x, y,f);
title(sprintf('The Surface and contour Plot'))
```

:The tteee1 function is here:

```
function fit = tteee1(x)
D = 2;
[ps, D] = size(x);
o=-50+100*rand(1,D);
x=x-repmat(o,ps,1);
fit = max(abs(x), [], 2);
end
```

when i run the program, it gives me this error:

??? Error using ==> contour at 73

Z must be size 2x2 or greater.

Error in ==> tteee at 20

contour(x,y,f);

What are the dimensions of your arrays?

Try this:

```
data = 20*rand([10,10])
figure;
contour(data);
```

```
cmin = -M;
cmax = M;
steps = 20;
c = linspace(cmin, cmax, steps); % Create the mesh
[x, y] = meshgrid(c, c); % Create the grid
o=-50+100*rand(1,n);
c = c - repmat(o,1,10);
f = arrayfun(@tteee1,x);
figure,
contour(x,y,f);
figure,
surfc(x, y,f);
```

This give a results as attached which looks different from the one i attached earlier which i am trying to achieve.

Do you know why they look different? Am trying to plot contour and contour surface of This function:

```
function f= tteee1(x)
D = 2;
[ps, D] = size(x);
o=-50+100*rand(1,D);
x=x-repmat(o,ps,1);
f = max(abs(x), [], 2);
end
```

I am not sure if arrayfun are appropriate for this task. If there are other appropriate method to achieve my goal, they are welcome.

PlotResult.pdf

```
for x = 1:20
for y = 1:20
hilbert(x, y) = 1/(x+y -1);
end
end
```

This is an example from the Matlab documentation.
```
cmin = -M;
cmax = M;
steps = 20;
c = linspace(cmin, cmax, steps); % Create the mesh
[x, y] = meshgrid(c, c); % Create the grid
%o=-50+100*rand(1,n);
%c = c - repmat(o,1,10);
for I=1:length(x)
for 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);
```

This still gives me the error:

Z must be size 2x2 or greater

The example you give involves x and y, which will surely work in a for loop, but in my case i only have one input which is x. How can it have the function f to output atleast a 2x2 matrix when only one input is given?

Are you really trying to do something with Genetic Algorithms and the Schwefel function?Yes, i am actually try to implement Estimation of Distribution Algorithm (EDA) in Evolutionary Computation to understand it. I am trying to test it on Benchmark functions in 2d and i am having trouble with plotting contour of some of them, and Schwefel function is one of them.

Accepted answer: 0 points for wish_C's comment #a39287043

for the following reason:

I solve it myself.

```
SWxlimits = [-100 100];
SWbias = [20 -20];
SWdx = (SWxlimits(2) - SWxlimits(1)) / 100;
SWN = floor((SWxlimits(2) - SWxlimits(1)) / SWdx) + 1;
Schwefel221objShifted = zeros(SWN, SWN);
SWi = 0;
for SWx = SWxlimits(1) : SWdx : SWxlimits(2)
SWi = SWi + 1;
SWk = 0;
for SWy = SWxlimits(1) : SWdx : SWxlimits(2)
SWk = SWk + 1;
Schwefel221objShifted(SWi,SWk) = max(abs(SWx-SWbias(1)), abs(SWy-SWbias(2)));
end
end
[SWx, SWy] = meshgrid(SWxlimits(1) : SWdx : SWxlimits(2));
figure;
contour(SWx,SWy,Schwefel221objShifted);
figure;
figure;
surfc(SWx,SWy,Schwefel221objShifted);
```

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