Check out linregress from scipy.stats module.  Not sure if it will handle dates.  Sample script below:

from scipy.stats import pearsonr from scipy.stats import linregress from matplotlib import pyplot as plt import numpy as np

sat = np.array([595,520,715,405,680,490,565]) gpa = np.array([3.4,3.2,3.9,2.3,3.9,2.5,3.5])

fig1 = plt.figure(1) ax = plt.subplot(1,1,1)

pearson = pearsonr(sat, gpa)

plt.scatter(sat,gpa, label="data")

# Get linear regression parameters slope, intercept, r_value, p_value, std_err = linregress(sat, gpa)

# Format the chart plt.xlabel("SAT Scores") plt.ylabel("GPA") plt.title("Scatter Plot with Linear Regression Fit\nY=a*X + b\na=%0.4f, b=%0.4f" % (slope, intercept)) plt.grid()

# Create linear regression x values x_lr = sat

# Create linear regression y values: Y = slope*X + intercept y_lr = slope * x_lr + intercept

print "Pearson correlation coefficient: ", pearson[0] print "Fit x-values: ", str(x_lr) print "Fit y-values: ", str(y_lr) print "Fit slope: ",slope print "Fit intercept: ", intercept plt.plot(x_lr, y_lr, label="fit") plt.legend()

plt.show()

Regards,
Daniel

On Jun 13, 2012 12:32 PM, "Chris Withers" <chris@simplistix.co.uk> wrote:
Hi all,

I have some time series of disk usage that I'd like to do a linear
regression on an plot on a nice graph with Mb used on the y-axis and
date on the x axis.

I tried to use pylab.polyfit(dates, usage) where:

dates = [datetime(x, y, z), datetime(a, b, c), ...]
usage = [12123234, 2234235235, ...]

...but polyfit doesn't like the dates.

How should I do this?

Any example of a nice plot and linear regression using matplotlib?

cheers,

Chris

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Simplistix - Content Management, Batch Processing & Python Consulting
            - http://www.simplistix.co.uk

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