[Solved] How to handle complex numbers in matplotlib

Question

Hello there! The code below draws the graph of a mathematical (for example: x**2 , 2*x+2, cos(x)), but when it comes to logarithms, the following error occurs:

Sample input:
ln(x)
2

Last 3 lines of Output:
File "../Playground//site-packages../Playground/", line 350, in __float__
raise TypeError("Cannot convert complex to float")
TypeError: Cannot convert complex to float

https://sololearn.com/compiler-playground/cNPQj468e5wk/?ref=app

Answer 1

Read the sympy documentation.
log() function returns complex result for negative numbers.

https://docs.sympy.org/latest/modules/functions/elementary.html#sympy.functions.elementary.exponential.log

"log represents the principal branch of the natural logarithm. As such it has a branch cut along the negative real axis and returns values having a complex argument:

Answer 2

Your y_list1 variable contains complex numbers.
This is definitely a mistake, you cannot plot complex numbers on a single real number axis, and the logarithm of any real number is not complex.
You should not overuse eval.

Answer 3

Got it! I just verified and I was able to debug my program... Thanks for your help!

Answer 4

So... What should I do then?...