Python Forum
how to select particular rows data from a array
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
how to select particular rows data from a array
I am new programmer to python. 
I have a text file having 360 rows and 190 columns of data. 
In matlab, if I load the text file and x_data will be variable of size 360x190 columns.
If I want to select 1 to 20 , 46 to 65, ... rows of data , I simply give 
x_data_train = xdata([1:20,46:65,91:110,136:155,181:200,226:245,271:290,316:335], :);
the resulting x_data_train will be the array of my desired. 

How can do that in python ? 

x_data = np.loadtxt('dataset_300mm.txt', unpack=True)
x_data_train = []
if I do using append operation , the resultant of the array is strange , it is array of 8 subsets of array for 20*192, but I want it to be one array 160*192
I think you should show more on original file structure.
It seems to me there should be an easier way to do this
however this should do it for what you have
x_data_train.append([0:19], [45:64])
assuming you want the first 20 elements which are numbered 0 - 19
and 20 more beginning with the 45th.
I am rather surprised that x_data_train.append(...) works at all. As x_data_train is a casual python list, append() takes only one argument - so you can make it work with either appending one array repeatedly or appending (or extending by) a list of your arrays. In either case you would end with a list (or even a list of lists) of arrays.

Numpy provides .concatenate(), that should work for you:

x_data_test = np.concatenate([x_data[0:20], x_data[45:64]])
Another way would be to construct  some "index" sequence and select on it - it could be list of  numbers of wanted rows or list of booleans.
thank you zivoni np.concatenate works

Possibly Related Threads…
Thread Author Replies Views Last Post
  Dropping Rows From A Data Frame Based On A Variable JoeDainton123 1 286 Aug-03-2020, 02:05 AM
Last Post: scidam
  Adding data in 3D array from 2D numpy array asmasattar 0 375 Jul-23-2020, 10:55 AM
Last Post: asmasattar
  How to shift data frame rows of specified column Mekala 0 446 Jul-21-2020, 02:42 PM
Last Post: Mekala
  Filter rows by multiple text conditions in another data frame i.e contains strings an Pan 0 468 Jun-09-2020, 06:05 AM
Last Post: Pan
  Select column between to dates CSV data PythonJD 0 411 Apr-14-2020, 12:22 PM
Last Post: PythonJD
  Read json array data by pandas vipinct 0 360 Apr-13-2020, 02:24 PM
Last Post: vipinct
  How can I convert time-series data in rows into column srvmig 0 349 Apr-11-2020, 05:40 AM
Last Post: srvmig
  Creating look up table/matrix from 3d data array chai0404 3 503 Apr-09-2020, 04:53 AM
Last Post: buran
  Select data from between two timestamps Makada 18 1,607 Feb-07-2020, 09:56 AM
Last Post: Makada
  Identifying consecutive masked values in a 3D data array chai0404 12 1,309 Feb-01-2020, 12:59 PM
Last Post: perfringo

Forum Jump:

User Panel Messages

Announcement #1 8/1/2020
Announcement #2 8/2/2020
Announcement #3 8/6/2020