undefined function or method 'impl' for input arguments of type 'function_handle'.

I keep putting in

f=@(x,y,z) x.ˆ2+y.ˆ2?z.ˆ2; 
corners=[?2 2 ? 2 2 ? 2 2]; 
subplot(2,2,1) 
impl(f,corners,1)
title(’c = 1’) 
subplot(2,2,2) 
impl(f,corners,.1) 
title(’c = .1’) 
subplot(2,2,3) 
impl(f,corners,0) 
title(’c = 0’) 
subplot(2,2,4) 
impl(f,corners,?.5) 
title(’c = ?.5’)

and I keep getting undefined function or method 'impl' for input arguments of type 'function_handle'.

what am i doing wrong?

Answer 1

[Walter Roberson]

What is it supposed to be? I don't see any "impl" function documented as part of MATLAB.

Answer 2

[Matt Fig]

Since you are the one using impl, whether it is a function or a variable, why not tell us what it is? If it is supposed to be a variable (I am guessing no, or you are using it incorrectly), where did you define it? If it is supposed to be a function, is it on your search path (probably not, but why do you think it should be)?

[Walter Roberson]

It can't be a variable: variables don't allow non-integer indexing. Well, not unless you design your own custom class.

[Matt Fig]

... which is why I said that it was being used incorrectly if it was a variable... you never know.

Answer 3

[Danilo Magistrali]

function out = impl(f, corners, c) % see impl.m in [Cooper]
xmin = corners(1); ymin = corners(3); zmin = corners(5);
xmax = corners(2); ymax = corners(4); zmax = corners(6);
x = linspace(xmin, xmax ,21); y = linspace(ymin, ymax, 21);
z = linspace(zmin, zmax, 21); [XX, YY, ZZ] = meshgrid(x, y, z);
W = feval(f, XX, YY, ZZ);
m = min(min(min(W))); M = max(max(max(W)));
sprintf( 'The max over this domain is % 5.5f %', M)
sprintf( 'The min over this domain is % 5.5f %', m)
if c < m | c > M
sprintf( 'In this domain, the function does not take on the value % 5.5f %', c)
else
[X, Y] = meshgrid(x, y);
dz = (zmax - zmin)/40;
for zz = zmin : dz : zmax
Z = feval(f, X, Y, zz);
con = contours(X, Y, Z, [c,c]);
nn = size(con, 2);
if nn > 0
j = 1; while j < nn
npairs = con(2, j);
xdata = con(1, j + 1: j + npairs);
ydata = con(2, j + 1: j + npairs);
plot3(xdata, ydata, zz + 0*xdata)
j = j + npairs + 1; hold on
end;
end;
end;
end
axis(corners);
xlabel('x'); ylabel('y'); zlabel('z'); hold off