Tag Archives: Python

Interpreting A/B Test using Python

Suppose we ran an A/B test with two different versions of a web page, and , for which we count the number of visitors and whether they convert or not. We can summarize this in a contingency table showing the … Continue reading

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Brand Positioning by Correspondence Analysis

I was reading an article about visualization techniques using multidimensional scaling (MDS), the correspondence analysis in particular. The example used R, but as usual I want to find ways to do it on Python, so here goes. The correspondence analysis … Continue reading

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PCA and Biplot using Python

There are several ways to run principal component analysis (PCA) using various packages (scikit-learn, statsmodels, etc.) or even just rolling out your own through singular-value decomposition and such. Visualizing the PCA result can be done through biplot. I was looking … Continue reading

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Running Tornado on dotCloud

To brush up my web development skills, I decided to try Tornado. I also wanted to find a hosting service of some sort for my projects, which must be cheap and developer friendly. There, dotCloud seemed very nice and I … Continue reading

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Searching for Nearest-Neighbors between Two Coordinate Catalogs

Say I have two catalogs of points, each in two-dimensional space. For each object in a catalog, I want to find the nearest object(s) in the other catalog. I can do this by computing the distances between every single unique … Continue reading

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Using Linux Shell Command within Python

If you just want to do some simple task, this would do:

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SciPy Weave Bug in Debian Squeeze

I was trying to remove a bottleneck by converting a portion of Python code into C++ via scipy.weave.inline, and encountered a bug. Here is my code: And this is what I get: Fortunately there is a fix: The fix for … Continue reading

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Comparing the Efficiencies of Gaussian Convolution Routines

These days I quite often need to convolve (i.e., smooth) 2D images by some Gaussian. There are quite a few routines that can do this with varying efficiencies. So I compared a couple of them. On my laptop, this script … Continue reading

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Suppressing Warnings in PyFITS

PyFITS is obviously a great Python package if you ever need to deal with data in astronomy. One thing that consistently annoyed me however was their use of warning messages.  For example, whenever you overwrite an existing FITS file, the … Continue reading

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Estimating Standard Deviation from N Data Points

In astronomy people often estimate a standard deviation in, say, background counts from the observed data themselves, since it is very difficult to know what true standard deviations are. Then the question is this: How many measurements (e.g., the number … Continue reading

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