Issue with np.diff()

[joyo44]

Trying to prevent increasing chord lengths spanwise during optimization with

opti.subject_to( np.diff(chords) <= 0 )

results in this error meassage from casadi:

*Traceback (most recent call last): np.diff(chords) <= 0 ^^^^^^^^^^^^^^^ File "C:\Users\LENOVO\anaconda3\envs\asb3\Lib\site-packages\aerosandbox\numpy\calculus.py", line 29, in diff result = _cas.diff(a) ^^^^^^^^^^^^ File "C:\Users\LENOVO\anaconda3\envs\asb3\Lib\site-packages\casadi\casadi.py", line 37257, in diff return _casadi.diff(args) ^^^^^^^^^^^^^^^^^^^ NotImplementedError: Wrong number or type of arguments for overloaded function 'diff'. Possible prototypes are: diff(DM,int,int) diff(SX,int,int) diff(MX,int,int) You have: '([MX])'**

chords = [MX(opti0_x_7), MX((opti0_x_7*opti0_x_6))]

AeroSandbox 4.2.3 Python 3.11.8

[carsonwmoon]

Ah, I see. If you put np.diff(chords) <= 0 in square brackets, it should work. Like this:

opti.subject_to(
     [np.diff(chords) <= 0]
)

Hope that helps! Let me know if it doesn't work and I'll debug it with ya.

[peterdsharpe]

Hi @joyo44,

This traceback says that you have attempted to apply np.diff() to a list, rather than an array-like object. To fix this, first convert the object you're trying to evaluate to an array-like object:

import aerosandbox.numpy

...

opti.subject_to(
    np.diff(np.array(chords)) <= 0
)