Error in python numpy

Question

I was trying to run a script which is written below. The focus is to print 'rab'.

from numpy import *
import numpy as np
import matplotlib.pyplot as plt
from scipy import interpolate


x = [64, 67, 70.459, 73, 76]
y = [0.697, 0.693, 0.694, 0.698, 0.702]
z = [0.748, 0.745, 0.747, 0.757, 0.763]


delT = 1

f = open('volume-temperature.dat', 'r')
V = []
for line in f:
        parts = line.split()
        if len(parts) > 1:
                #print parts[1]
                V.append(parts[1])
f.close()

for M in range(0,5):
        T = 0+M*delT
        if M == 0:
            rab = np.interp(V[M], x, y)
            print rab
        else:
            print M

The problem is while printing 'rab' I am geting this error:

return compiled_interp(x, xp, fp, left, right)
ValueError: object of too small depth for desired array

It looks some fundamental error, But as I am new in Python, so a little help would be appreciated. N.B. V[M] for M = 0 is 70.31

Aside: Since you're new I'll give you an important warning: don't use star imports like from numpy import *. While it can be convenient sometimes it replaces certain built-in functions like sum with numpy's versions which behave very differently (i.e. can give the opposite results) in some circumstances. — DSM
– DSM, Commented Sep 18, 2014 at 17:05
I would add to DSM not to import it twice use either from numpy import * or import numpya as np — llrs
– llrs, Commented Sep 18, 2014 at 17:06
If I just put the 70.31 instead of V[M], then it is working. But since I have a series of values so, in any case I have to use V[M]. — Tanmoy Chakraborty
– Tanmoy Chakraborty, Commented Sep 18, 2014 at 17:12
@TanmoyChakraborty what happens when you print V[M] after you loop through the file? Also, I would advise learning how to use the "with as" file iterator, because it's much easier and cleaner :-) (the info in the link is towards the bottom of that section) — dantiston
– dantiston, Commented Sep 18, 2014 at 17:37

Warren Weckesser · Accepted Answer · 2014-09-18 17:49:14Z

3

Your list V is a list of strings. You must convert these values to floating point numbers before passing them to np.interp.

You could change this:

        V.append(parts[1])

to this:

        V.append(float(parts[1]))

edited Sep 18, 2014 at 17:49

answered Sep 18, 2014 at 17:43

Warren Weckesser

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1 Comment

Tanmoy Chakraborty Over a year ago

Many many thanks Warren for the correct solution. It's working now. Thanks!!

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