[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## mesh and meshdom bugs?

**From**: |
Joao Cardoso |

**Subject**: |
mesh and meshdom bugs? |

**Date**: |
Fri, 3 Nov 1995 05:51:17 +0100 (MET) |

Hi,
If I am correct, there is a bug in `meshdom' and `mesh'.
In `meshdom' for some strange reason the y vector is calculated backward:
y = y (ylen:-1:1); # jc: this line seems to be incorrect
y = y (1:ylen); # jc: it should(?) be this way
in `mesh', the following comparision also seems to be wrong:
if (xlen == rows (z) && ylen == columns (z)) # wrong ?
if (ylen == rows (z) && xlen == columns (z)) # right ?
The following "code" tryes to show both problems. It is the `sombrero' ploted
in the first quadrant. The first error message shows the error in `mesh'.
Now, watching the plot, one can see that the maximum of the function in not
at (0,0), showing the incorrection in `meshdom'.
octave:1> n=5;
x=linspace (0, 15, 5*n)';y=linspace (0,5, n)';
[xx, yy] = meshdom(x, y);
r = sqrt (xx .^ 2 + yy .^ 2) + eps;z = sin (r) ./ r;
mesh(x,y,z)
error: mesh: rows (z) must be the same as length (x) and
columns (z) must be the same as length (y)
octave:2> n=5;
x=linspace (0, 15, 5*n)';y=linspace (0,5, n)';
[xx, yy] = meshdom(x, y);
r = sqrt (xx .^ 2 + yy .^ 2) + eps;z = sin (r) ./ r;
mesh(x,y,z') <--- note the transposition of z, for this to work
As I don't use this kind of ploting I am not absolutly shure of my reasons...
Thanks,
Joao

**mesh and meshdom bugs?**,
*Joao Cardoso* **<=**