[Tutor] Appending an extra column in a data file

[Sayan Chatterjee]

Hi Andre,

Is it that? We can have different plots and hence animation from a single
data file.Very good!...if you have some time in your disposal, it will be
kind of you to illumine in this matter...may be some useful link will do.

I have written this small code from scratch,there's no 'get it to work'
business...:)

Here is the total code...not attaching as you might have problem opening
random files from internet....:)

#!usr/bin/python

import numpy as np
import matplotlib.pyplot as plt
import itertools as i
import pylab

K = 3.14
t = 0

# Allotment of particles

pp_init = np.linspace(0,1.99799799,999)

print pp_init

# Velocity array

while t < 1:


  pp_za = pp_init + t*K*np.sin(K*pp_init)

# Periodic Boundary Condition

  for i in range(0,999):

    if pp_za[i] < 0:
      pp_za[i] = 2 - abs(pp_za[i])
    if pp_za[i] > 2:
      pp_za[i] = pp_za[i] % 2

  pv_za = +K*np.sin(K*pp_init)

  fname = 'file_' + str(t) + '.dat'

# Generating dataset for Phase Space diagram
  np.savetxt(fname, np.array([pp_za,pv_za,t]), '%f')

  t = t + 0.01

# Plot using Matplotlib

i = 0

while i < 1:
  fname = 'file_' + str(i) + '.dat'
  f=open(fname,"r")
  x,y = np.loadtxt(fname, unpack=True)
  #plt.plot(x,y,linewidth=2.0)
  plt.scatter(x,y)
  plt.ylim(-8,8)
  plt.xlim(0,2)
  plt.ylabel('Velocity')
  plt.xlabel('X')
  pylab.savefig(fname + '.png')
  plt.cla()
  f.close()
  i = i  + 0.001

Regards,
Sayan




On 10 April 2013 23:36, Andre' Walker-Loud <walksloud at gmail.com> wrote:

> Hi Sayan,
>
> > Yup it's exactly what I want!
> >
> > I want many data files,not one...to make an animation out of it. For a
> data file t is constant.
>
> You should not need many data files to make an animation.  If you write
> your loops correctly, you can take a single data file with all the data.
>  If you are using code you did not write, and just want to get it to work,
> I understand that, but would encourage you also to figure out how to do it
> all with single data file.  Less files makes a files system and user
> happier.
>
> > the solution you have just mentioned i.e np.array([t,pp_za,pv_za]) is
> giving the following error:
> >
> >
> > Traceback (most recent call last):
> >   File "ZA_Phase_Plot.py", line 38, in <module>
> >     np.savetxt(fname, np.array([pp_za,pv_za,t]).T, '%f')
> >   File "/usr/lib/python2.7/dist-packages/numpy/lib/npyio.py", line 979,
> in savetxt
> >     fh.write(asbytes(format % tuple(row) + newline))
> > TypeError: float argument required, not numpy.ndarray
> >
> > What to do? :-|
>
> There are pieces of the code snipet you sent which are not defined, so it
> is not clear why you are getting this error.  How long is the file
> "ZA_Phase_Plot.py"?  At least you can send from line 0 to where you did
> before, so all the variables are defined.  That should help.
>
> Andre
>
>
>
>


-- 


--------------------------------------------------------------------------
*Sayan  Chatterjee*
Dept. of Physics and Meteorology
IIT Kharagpur
Lal Bahadur Shastry Hall of Residence
Room AB 205
Mob: +91 9874513565
blog: www.blissprofound.blogspot.com

Volunteer , Padakshep
www.padakshep.org
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