Fast Fourier Transform

import csv
import plotly
import plotly.offline as offline
import plotly.graph_objs as go
import scipy
import numpy

time = []
voltage = []

data_file = open("data_0.dat")
with data_file as csvfile:
    reader = csv.reader(data_file, delimiter = ",")
    for row in reader:
        time.append(row[0])

        voltage.append(row[1])

N = len(voltage)
#rate = 2500
array = numpy.array(voltage)

xplot = time
yplot = numpy.fft.fft(voltage)
freq = numpy.fft.fftfreq(N, .01923)

mask = freq > 0

trace_accel = go.Scatter(
    x = freq[mask],
    y = numpy.abs(yplot[mask]),
    name = 'Ampl vs Freq',
    line = dict(
        color = ('rgb(255,0,0)'),
        width = 1))

data = [trace_accel]
layout = dict(title = "Amplitude vs. Frequency",
    xaxis = dict(title = 'Frequency (Hz)'),
    yaxis = dict(title = 'Amplitude'),
    font = dict(size=16))

fig = dict(data=data, layout=layout)

offline.plot(fig,
    image_height='1275', image_width='1650', image='png')