grdvector with polar coordinates
|Target version:||Candidate for next bugfix release|
I found that some errors may happen when using grdvector to handle velocity field in polar coordinates.
For example, suppose file 'vel_x' and 'vel_y' respectively contains the x and y component of velocity field, then every thing is right if cartesian coordinates is used (see file 'draw' and the result shows in 'draw.png'). However, the result may be wrong if polar coordinates is adopted, because as you can see from 'draw_polar.png', the 3 arrows in degree 45 should not perpendicular to the theta direction (the script for polar coordinates is in file 'draw_polar').