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#!/usr/bin/env python3
# -*- coding:utf-8 -*-
"""Plot for integrand of gamma function with shifting terms."""
if __name__ == "__main__":
import os
from pathlib import Path
import matplotlib as mpl
import matplotlib.pyplot as plt
import numpy as np
mpl.rcParams.update(
{
"mathtext.fontset": "stix",
"font.family": "serif",
"font.serif": "TeX Gyre Termes",
}
)
EPSILON = 1e-12
xlims = np.array([-3, 3])
root = str(Path(__file__).parent)
img_path = f"{root}/../images"
os.makedirs(img_path, exist_ok=True)
t = np.logspace(*xlims, 1001)[:, None]
z = np.array([-1, -0.5, 0.0, 0.5, 1, 2, 3, 4, 4.5])
e = np.exp(-t)
r = t ** z * e
fig, ax = plt.subplots(num=2, clear=True, constrained_layout=True, figsize=(4, 2.4))
ax.semilogx(t, r)
# ax.plot(t,np.exp(-t))
ax.set_xlim(10 ** (-2), 20)
ax.set_ylim(1e-3, 10)
ax.set_xlabel(r"$x$")
# ax.set_ylabel(r"$x^z e^{-x}$")
ax.grid(1, "both")
labels = [f"$z={zi: 3.1f}$" for zi in np.squeeze(z)]
ax.legend(labels, ncol=2, loc="upper left", fontsize="small")
# fig.savefig(f"{img_path}/integrand_exp.pgf")
fig.savefig(f"{img_path}/integrand_exp.pdf")
# plt.show()
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