在x轴上以奇数和负数绘制刻度线-Python

Question

I have a plot where I need to change the ticks in the xaxis, this way: the x values have to range from 0 to 32 and THEN (CONSECUTIVELY, WITHOUT INTERRUPTION) from -31 to -1.

Here is the code to produce such an xaxis, at least as an array:

nyquist = int(64/2) +1
xaxis1 = np.arange(1, nyquist)
xaxis2 = np.arange(-(int(nyquist)-1), 0)
xaxis = np.concatenate((xaxis1, xaxis2))

The result for xaxis is:

array([  1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,
        14,  15,  16,  17,  18,  19,  20,  21,  22,  23,  24,  25,  26,
        27,  28,  29,  30,  31,  32, -31, -30, -29, -28, -27, -26, -25,
       -24, -23, -22, -21, -20, -19, -18, -17, -16, -15, -14, -13, -12,
       -11, -10,  -9,  -8,  -7,  -6,  -5,  -4,  -3,  -2,  -1])

Then imagine that the curve to plot is stored in:

curve = np.zeros(64, float)
for k in range(1, nyquist):
    curve[k] = np.exp(-(k**2))
for k in range(int(n/2+1), n):
    curve[k] = curve[n-k]

OK, now I need to create a plot, but with the ticks given by "xaxis" (it's OK if I don't plot all the 64 values, but just 6 of them, for example, but the order must be respected, making explicit the presence of NEGATIVE values in that strange order). That's what I used to do, but this does not produce what wanted:

fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(np.arange(64), curve, 'ro-')

because obviously this would put on the x-axis 64 values ranging from 0 to 63, not what I need.

How can I do?

EDIT:

I am providing a piece of runnable code.

import matplotlib as plt
import numpy as np

n = 64
nyquist = int(n/2) +1
xaxis1 = np.arange(1, nyquist)
xaxis2 = np.arange(-(int(nyquist)-1), 0)
xaxis = np.concatenate((xaxis1, xaxis2))

curve = np.zeros(n, float)
for k in range(1, nyquist):
    curve[k] = np.exp(-(k**2))
for k in range(int(n/2+1), n):
    curve[k] = curve[n-k]

fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(np.arange(64), curve, 'ro-')
plt.savefig('curve.svg')

This only produces the "wrong" plot, the one with only positive x values

Answer 1

You can use xticks as:

plt.xticks(range(len(xaxis)), xaxis)

You can also rotate the xtick values in case of tick overlapping as:

plt.xticks(range(len(xaxis)), xaxis, rotation='vertical')

You can create xaxis in this simple way:

>>> range(1,33)+range(-32,0, 1)
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, -32, -31, -30, -29, -28, -27, -26, -25, -24, -23, -22, -21, -20, -19, -18, -17, -16, -15, -14, -13, -12, -11, -10, -9, -8, -7, -6, -5, -4, -3, -2, -1]