Could not convert String to float in numpy ndarray

Question

I have been doing some reading from fer 2013 csv file containing three columns emotion, pixel value and usage. the pixel value is said to have given in string format and I want to rescale my pixel values from 0-255 to between 0-1 , so I need to convert it to int/float and then only I would be able to do any mathematical operations on them.

I first tried to read the csv file using pandas read_csv function and then using iloc I read the value of the pixel value in a variable called x_tr. Then upon printing its value it shows its d type as object.confused on that too.x_tr is numpy ndarray then how should I convert it into integral value. I tried the x_tr.astype(np.float) but it gave up the error as mentioned in the code.

x_tr = train.iloc[:,1].values
x_tr

what I tried to convert to float

x_tr = train.iloc[:,1].values
x_tr = x_tr.astype(np.float)

and what I've got as error

Please Help.

They are from a set of 28k images with each image being a size of 48*48 how could I post them as code?? — Somil Rastogi
– Somil Rastogi, Commented Apr 20, 2019 at 10:25
Post a sample; otherwise, how can we reproduce your issue and offer concrete advice? — desertnaut
– desertnaut, Commented Apr 20, 2019 at 10:26

Supratim Haldar · Accepted Answer · 2019-04-20 10:16:10Z

1

Don't convert your pixel into an array, instead treat it as a simple string. Then use numpy.fromstring() method. Here's an example for reference.

>>> s = '1 2 3 4'
>>> f = np.fromstring(s, dtype=float, sep=' ')
>>> f
array([1., 2., 3., 4.])

answered Apr 20, 2019 at 10:16

Supratim Haldar

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