Re: [Tutor] Plotting subsets of data
Perfect, thank you Danny!
On Mon, Dec 8, 2014 at 3:49 PM, Danny Yoo wrote:
> On Mon, Dec 8, 2014 at 7:48 AM, Colin Ross
> wrote:
> > Good afternoon,
> >
> > I am using the following to code to plot the output from an optical
> encoder:
>
> Hi Colin,
>
> Matplotlib is a third-party library, so you may also consider asking
> the matplotlib folks.
>
> From a brief look at:
>
>
> http://matplotlib.org/1.4.2/users/pyplot_tutorial.html#working-with-multiple-figures-and-axes
>
> it appears that you can override the default axis, and specify xmin,
> ymin, xmax, and ymax values.
>
> http://matplotlib.org/1.4.2/api/pyplot_api.html#matplotlib.pyplot.axis
>
> For your particular case, you may want to just limit your x axis, in
> which case xlim() might be appropriate.
>
> http://matplotlib.org/1.4.2/api/pyplot_api.html#matplotlib.pyplot.xlim
>
>
> If all else fails, just filter your data before submitting it to the
> grapher. The program loads data here, using loadtxt
> (http://docs.scipy.org/doc/numpy/reference/generated/numpy.loadtxt.html):
>
> data = np.loadtxt('2014_12_04-16_30_03.txt',skiprows = 0 ,usecols =
> (0,1))
>
> and it's just a numpy array: you can manipulate numpy arrays. See:
>
>
> http://stackoverflow.com/questions/26154711/filter-rows-of-a-numpy-array
>
> as an example of an approach.
>
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Re: [Tutor] Plotting subsets of data
On Mon, Dec 8, 2014 at 7:48 AM, Colin Ross wrote:
> Good afternoon,
>
> I am using the following to code to plot the output from an optical encoder:
Hi Colin,
Matplotlib is a third-party library, so you may also consider asking
the matplotlib folks.
>From a brief look at:
http://matplotlib.org/1.4.2/users/pyplot_tutorial.html#working-with-multiple-figures-and-axes
it appears that you can override the default axis, and specify xmin,
ymin, xmax, and ymax values.
http://matplotlib.org/1.4.2/api/pyplot_api.html#matplotlib.pyplot.axis
For your particular case, you may want to just limit your x axis, in
which case xlim() might be appropriate.
http://matplotlib.org/1.4.2/api/pyplot_api.html#matplotlib.pyplot.xlim
If all else fails, just filter your data before submitting it to the
grapher. The program loads data here, using loadtxt
(http://docs.scipy.org/doc/numpy/reference/generated/numpy.loadtxt.html):
data = np.loadtxt('2014_12_04-16_30_03.txt',skiprows = 0 ,usecols = (0,1))
and it's just a numpy array: you can manipulate numpy arrays. See:
http://stackoverflow.com/questions/26154711/filter-rows-of-a-numpy-array
as an example of an approach.
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[Tutor] Plotting subsets of data
Good afternoon,
I am using the following to code to plot the output from an optical encoder:
import numpy as np
from numpy import ma, logical_or
import pylab
from pylab import *
import matplotlib.pyplot as plt
from matplotlib.ticker import AutoMinorLocator
import sys
# Defining x and y minorlocator
xminorLocator=AutoMinorLocator()
yminorLocator=AutoMinorLocator()
# Load data from .txt file
data = np.loadtxt('2014_12_04-16_30_03.txt',skiprows = 0 ,usecols = (0,1))
print "\n Chopper Test for X-SPEC Prototype"
print "\n Time (sec) Pos (deg)"
print data
# Place column data in array to be plotted
time = np.array(data[:,0])
print "Time (sec):"
#print time
pos = np.array(data[:,1])
print "Position (deg):"
print pos
# Setting minor ticks
ax = plt.subplot(111)
ax.xaxis.set_minor_locator(xminorLocator)
ax.yaxis.set_minor_locator(yminorLocator)
#Plotting commands.
subplot(2,1,1)
plot(time, pos, 'ro')
title('Encoder Output')
ylabel('Pos (deg)')
subplot(2,1,2)
plot(t_small, pos, 'ro')
xlabel('Time (sec)')
ylabel('Pos (deg)')
show()
The desired result is a square wave, but this is not readily available from
the plot (see attached). For the subplot(2,1,2) I would like to plot the
output over a 5 second interval so that the behaviour becomes more evident.
Can someone please advise me as to the easiest way isolate the first 5
seconds of data?
Thank you.
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