Value Error: could not broadcast input array from shape (857,3) into shape (857)

Question

I've been trying to plot a database that I parsed from a text file into a numpy array. The array has 857 rows.

This error keeps popping up, I dont understand what it means.

import matplotlib
import matplotlib.pyplot as plt
import numpy

def parseFile(file):
    F = open(file)
    n = len(F.readlines())  #no. of lines in file
    numpyMat = numpy.zeros((n,3)) # create numpy matrix
    classLabelVector = []
    F = open(file)          # from the beginning again
    i = 0
    for line in F.readlines():
        line = line.strip()
        listFromLine = line.split()
        numpyMat[i,:] = listFromLine[0:3]   # 3 is the no. of variables/columns
        classLabelVector.append(int(listFromLine[-1]))
    i+=1
    return numpyMat, classLabelVector

dataMatrix = parseFile('kiwibubbles_tran.txt')

fig = plt.figure()

ax = fig.add_subplot(111)
ax.scatter(dataMatrix[:1], dataMatrix[:2])   # Error

plt.show()

Error: ValueError: could not broadcast input array from shape (857,3) into shape (857)

maybe you want it to say: `ax.scatter(dataMatrix[:,1], dataMatrix[:,2])` — Crispin, Feb 27 '17 at 11:24
You return a tuple from the parse file function but you don't unpack it when calling the function, i.e. your `dataMatrix` is not the matrix itself but a tuple that also contains the label vector. — a_guest, Feb 27 '17 at 11:37
@waterboy5281 That gives me a Type Error, saying that the tuple indices must be integers or slices — crater_creater, Feb 27 '17 at 11:40

score 0 · Accepted Answer · answered Feb 27 '17 at 11:56

Your dataMatrix is a tuple, so you have two options:

Take the results of the fuction in two different variables:

numpyMat, classLabels = parseFile('kiwibubbles_tran.txt')
fig = plt.figure()

ax = fig.add_subplot(111)
ax.scatter(numpyMat[:,1], numpyMat[:,2])

plt.show()

Plot only the numpyMat from the tuple:

dataMatrix = parseFile('kiwibubbles_tran.txt')
fig = plt.figure()

ax = fig.add_subplot(111)
ax.scatter(dataMatrix[0][:,1], dataMatrix[0][:,2])

plt.show()

That helped. Thanks a lot! :D – crater_creater Feb 28 '17 at 08:35 — crater_creater, Feb 28 '17 at 08:35

Value Error: could not broadcast input array from shape (857,3) into shape (857)

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