[Tutor] Appending an extra column in a data file

[Sayan Chatterjee]

Hi Andre,

Well,this is the concerned snippet of the code:


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

And the sample data generated is :

0.105728 0.098678
0.126865 0.118406
0.147998 0.138128
0.169126 0.157845
0.190247 0.177556
0.211362 0.197259
0.232469 0.216955
0.253567 0.236643
0.274657 0.256321
0.295737 0.275989
0.316806 0.295646

Precisely what I want is, I want to add the 't' (over which the while loop
is run) in the 3 rd column. 't' is float and constant for each looping. If
you know what a phase plot is(doesn't matter if you don't), I want to see
the phase plot evolving with time. Thus the need of a time axis and hence
plot with V(velocity-Yaxis), X ( Position -X axis) and t (Time-Z axis).

I hope your first example might help.Though,I think,I need some tweaking to
fit to my needs.

Regards,
Sayan


On 10 April 2013 22:38, Andre' Walker-Loud <walksloud at gmail.com> wrote:

> Hi Sayan,
>
> > Thank Andre for your prompt answer.
>
> No problem.
>
> > I'll figure out the plotting issue once the dat files are made. So it's
> the primary concern.
> > For an example I am attaching a dat file herewith. The two columns here
> are 2 numpy arrays.I want to add a third column, to be precise, I want to
> print a parameter value on the third column of the file.
>
> Let me try again.
> The reason the matplotlib list would be a better place is this is a
> general python list, and most people are not familiar with numpy.  However,
> most people who use matplotlib are familiar with numpy.
>
> I am hoping you can describe precisely the structure of the data.  Maybe
> show a little code on how it is created, or how you access it.  I am not
> keen to open "random" files from the internet.  As two examples of how I
> think your code might be packed
>
> 1/
> '''
> x = numpy.zeros([10]) # 1D numpy array of dimension 10
> y = numpy.zeros([10]) # 1D numpy array of dimension 10
> your_data = []
> your_data.append(x)
> your_data.append(y)
> '''
>
> so now your data is a table with two entries, and each entry is a numpy
> array.
> You have in mind adding a third entry to the table with just floats.
>
> 2/
> '''
> your_data = numpy.zeros([10,10]) # initialize a 2D numpy array with all
> zeros
> for i in range(your_data.shape[0]):
>     for j in range(your_data.shape[1]):
>         your_data[i,j] = data[i][j] # I am assuming the data is imported
> already and called data and is in a python list/table format
> '''
>
> Now you want to make a new column or row for your data file, which
> contains floats.  Well, all the entries inside the numpy array are already
> floats, so it is not clear to me why you want a new column that is not a
> numpy array. So it would be nice if you could precisely describe what you
> currently have and what you want.
>
>
> Hope this helps,
>
> 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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