matplotlib- Y and X axis are swapped

Question

I'm trying to plot a spectrogram. I am using the imshow in matplotlib.

The problem is this, I am reading the data from a text file generated in C++ (it essentially creates a 2D vector and stores this into a text file) I then read in the text file and plot.

Below is the output of the plot I've generated (from C++ and imported into python):

Here is a plot of a spectrogram, actually in Python (using matplotlib):

As you can see, the x and y axis are swapped, which is giving me the wrong shape for the actual spectrogram.

Why could this be? For example, could I be reading in the data wrong in the first place and this has happened? Or, could it be that I'm not setting the x, y axis itself?

Any help would be greatly appreciated

EDIT:

I read the array using this function:

def split_at_empty_lines(filename):

with open(filename) as f:
    arr = [] 
    for line in f:
        if not line.strip() and arr:
            yield arr 
            arr = []
        elif line.strip(): arr.extend(float(x) for x in line.split())
    if arr: yield arr;

The spectrogram is produced by doing the following:

a = list(split_at_empty_lines("file.txt"); 

hm = ax.imshow(a, interpolation='nearest',origin='lower',aspect='auto')

Here is the result:

[[ 26.9287  30.9089  34.9285 ...,  23.016   28.9027  36.4073]
 [ 26.7964  26.8524  32.7296 ...,  22.9524  28.6145  33.7204]
 [ 26.4222  27.0941  29.094  ...,  22.5309  27.6803  26.7073]
..., 
[ 25.9362  25.8307  29.7039 ...,  22.0084  25.9855  28.9602]
[ 26.4222  27.0941  29.094  ...,  22.5309  27.6803  26.7073]
[ 26.7964  26.8524  32.7296 ...,  22.9524  28.6145  33.7204]]

Here is the results:

I don't know why I'm getting such different results.

Answer 1

If you are reading the data with numpy into an ndarray you can transpose the array before plotting.

import numpy as np
a = np.array(split_at_empty_lines("file.txt"))
print(a.T)

should produce

array([[1, 4],
       [2, 5],
       [3, 6]])