contour plot with python loop and matplotlib

Question

I can't figure out what's preventing me from getting a contour plot of this cost function. After much trial and error, I'm getting:

ValueError: zero-size array to reduction operation minimum which has no identity

If I print J it doesn't give me any values, just a 100x100 array full of nan. Is that the reason? J should be full of cost values, right? Thanks so much for any help.

X,y,ComputeCost = defined earlier and 90% sure not the problem
theta_zero = np.linspace(-10,10,100)
theta_one = np.linspace(-1,4,100)
L,Q = np.meshgrid(theta_zero,theta_one)
J = np.zeros((len(theta_zero),len(theta_one)))

for i in range(0,len(theta_zero)):
    for j in range(0,len(theta_one)):
        t = DataFrame([theta_zero[i],theta_one[j]])
        J[i,j] = ComputeCost(X,y,t)

plt.contour(L,Q,J)

user3666197 · Accepted Answer · 2014-08-29 23:45:41Z

1

If J is just nans, then the problem is in the way you're generating J and not the contour() call.

edited Aug 29, 2014 at 23:45

user3666197

1

answered Aug 29, 2014 at 23:32

aardvark

113 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user2891518 Over a year ago

Thanks. I guess the next question is why are the for loops leaving me with a J full of nan's? As is, the code spits out all the values--one per line--before giving me the error when trying to plot the contour. Not sure why they aren't being stored in J.

aardvark Over a year ago

So, if you use an intermediate variable it comes out at non-nan? i.e.: foo = ComputeCost(X,y,t) print foo J[i,j] = foo If foo prints out as non-non, then I'm at a loss too.

user2891518 Over a year ago

If I create some other variable, Z, and set it equal to a 100X100 array, then I get the same error with Z[i,j] in the loop as I do with J[i,j].

Collectives™ on Stack Overflow

contour plot with python loop and matplotlib

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related