The function contour has different outputs in Scilab than in MATLAB? - matlab

Question

I'm trying to convert this Matlab code to Scilab, but I have some problems.
clear all; clc;
c0 = 0.8;
c1 = 1.3;
c11 = -6.1;
c12 = -0.6;
c2 = 1.7;
c22 = -1.7;
g = 0.05;
d = 0.01;
x1 = -9;
x2 = 8;
k = 1;
kmax = 100;
x1trace = [x1];
x2trace = [x2];
i = 2;
while k < kmax
gr1 = c1 + c12*x2 + 2*c11*x1;
x1 = x1 + g*gr1
x1trace(i) = x1;
x2trace(i) = x2;
i = i + 1;
gr2 = c2 + c12*x1 + 2*c22*x2;
x2 = x2 + g*gr2
x1trace(i) = x1;
x2trace(i) = x2;
i = i + 1;
if sqrt(gr1^2 + gr2^2) <= d;
break;
end
k = k + 1;
end
x = -10:0.1:10;
y = -10:0.1:10;
[X, Y] = meshgrid(x, y);
Z = c0 + c1*X + c2*Y + c12*X.*Y + c11*X.^2 + c22*Y.^2;
[C, h] = contour(X, Y, Z);
clabel(C, h);
hold on;
plot(x1trace, x2trace, '-');
text(x1trace(1) + 0.2, x2trace(1) + 0.5, 'M0');
text(x1 + 2, x2, ...
strvcat(['x1 = ' (num2str(x1))], ...
['x2 = ' (num2str(x2))], ...
['k = ' (num2str(k))]));
hold off;
I get an error for this line:
[C, h] = contour(X, Y, Z);
Wrong number of output arguments.
What should I change to fix it? Are there also any other errors in the code ?

Answer 1

You should have roughly the samed rendering with the following Scilab code. Scilab's contour needs (in the 4th argument) the number of level curves or the values themselves. In addition, you should use ndgrid instead of meshgrid:
clear clc;
c0 = 0.8;
c1 = 1.3;
c11 = -6.1;
c12 = -0.6;
c2 = 1.7;
c22 = -1.7;
g = 0.05;
d = 0.01;
x1 = -9;
x2 = 8;
k = 1;
kmax = 100;
x1trace = [x1];
x2trace = [x2];
i = 2;
while k < kmax
gr1 = c1 + c12*x2 + 2*c11*x1;
x1 = x1 + g*gr1
x1trace(i) = x1;
x2trace(i) = x2;
i = i + 1;
gr2 = c2 + c12*x1 + 2*c22*x2;
x2 = x2 + g*gr2
x1trace(i) = x1;
x2trace(i) = x2;
i = i + 1;
if sqrt(gr1^2 + gr2^2) <= d;
break;
end
k = k + 1;
end
x = -10:0.1:10;
y = -10:0.1:10;
[X, Y] = ndgrid(x, y);
Z = c0 + c1*X + c2*Y + c12*X.*Y + c11*X.^2 + c22*Y.^2;
clf
gcf.color_map=parulacolormap(8)($:-1:1,:)
contour(x, y, Z,0:-100:-700);
plot(x1trace, x2trace, '-');
xstring(x1trace(1) + 0.2, x2trace(1) + 0.5, 'M0');
xstring(x1 + 2, x2, ...
['x1 = '+string(x1)
'x2 = '+string(x2)
'k = '+string(k)]);