From fd0f784f5c9951543d06c5be8c6508fbfe0924e2 Mon Sep 17 00:00:00 2001
From: Aaron LI <aly@aaronly.me>
Date: Mon, 28 Jan 2019 16:51:03 +0800
Subject: utils/analyze: Add logfit()
This function helps fit the index of a scaling relation.
---
fg21sim/utils/analyze.py | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/fg21sim/utils/analyze.py b/fg21sim/utils/analyze.py
index ad9f1b4..f33f65c 100644
--- a/fg21sim/utils/analyze.py
+++ b/fg21sim/utils/analyze.py
@@ -1,5 +1,5 @@
-# Copyright (c) 2017 Weitian LI <weitian@aaronly.me>
-# MIT license
+# Copyright (c) 2017,2019 Weitian LI <wt@liwt.net>
+# MIT License
"""
Utilities to help analyze the simulation results.
@@ -77,3 +77,28 @@ def countdist_integrated(x, nbin, log=True, xmin=None, xmax=None):
binedges = np.exp(binedges)
return (counts, bins, binedges)
+
+
+def logfit(x, y):
+ """
+ Fit the data points with: y = a * x^b
+
+ Parameters
+ ----------
+ x, y : list[float]
+ The data points.
+
+ Returns
+ -------
+ coef : (a, b)
+ The fitted coefficients.
+ fp : function
+ The function with fitted coefficients to calculate the fitted
+ values: fp(x).
+ """
+ logx = np.log(x)
+ logy = np.log(y)
+ fit = np.polyfit(logx, logy, deg=1)
+ coef = (np.exp(fit[1]), fit[0])
+ fp = lambda x: np.exp(np.polyval(fit, np.log(x)))
+ return coef, fp
--
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