来自python中带列文本文件的2D数组

Question

I am new to python and working on a script that will create a 2D array from a text file. The file has 4 columns, like so:

P    F    T    S
0    0    0    0.227321
0    0    1    0.0380602
0    0    2    -0.804958
0    0    3    0.271401

Where P, F, T, and S are the polarization state, frequency, time, and signal strength, respectively. I want to create a 2D matrix of S such that they will have x and y coordinates of the corresponding T and F values (Ignoring P). I know how to create a matrix from text, but that just creates a 4 by n matrix that is identical in form to the text file. How can I generate the 2D matrix I need?

EDIT: I meant ignoring P, not S.

Answer 1

Suppose your text file is named data.txt

import numpy as np
dat = np.loadtxt( 'data.txt' )

now dat[0,:] will be the first row and dat[:,2] will be the third column and so on. Note that you will have to add a comment character to the first line # of your file so it wont be readin by loadtxt .

ii = dat[:,1].astype( np.int )  # this is the F column as ints
jj = dat[:,2].astype( np.int )  # this is the T column as ints

nx = max(ii) + 1
ny = max(jj) + 1
d = np.zeros( (nx,ny) )

n = 0
for i,j in zip(ii,jj):
    d[i,j] = dat[n,3]
    n += 1

Now d will have the values of S in the locations specified by the columns F and T and 0's elsewhere.

Answer 2

How about this sample:

with open("matrix.txt", "r") as df:
    txt = df.read()
    items = txt.split()
    items = [float(n) for n in items]
    data = zip([i for i in items[1::4]], [i for i in items[2::4]], [i for i in items[3::4]])
    print(data)
    print(data[1][2])

Output:

[(0.0, 0.0), (0.0, 1.0), (0.0, 2.0), (0.0, 3.0)]

1.0

"data" now includes X y coordinates and the value. you should have all you need

Answer 3

1. Read in the file and save all of the data into a 4 by n matrix as you said.
2. Then loop through each row and save the appropriate S or P value as array[F][T]=S