Category Archives: Uncategorized

Puzzle: The Wolf, the Goat, and the Cabbage

In this post I’ll present a solution to a puzzle using Python. I think the primary value of this post is that it provides an example of how to translate an objective and a set of constraints into data structures and functions that can be interpreted by a computer. This problem breaks down into two interrelated parts:

  1. Translate the problem into data structures and functions
  2. Choose a strategy for finding the solution

Continue reading

Remove a Partition on a USB Drive in Windows

If you create a bootable USB flash drive for installing linux on a machines, you may have trouble reformatting it later in Windows. It is possible to create a bootable USB in such a way that the Windows reformatting utility, obtained by right-clicking on the drive and selecting Format…, does not see the partition containing the bootloader. In such a situation, you may have a 8GB drive, but the reformatting utility only sees 6GB, and reformatting will not recover the original 8GB of space.

Continue reading

Classical Hypothesis Testing, Statistical Power, and Type-II Errors

This is one of the fundamental tasks in science. You do a study, and then you have to determine if there is a statistically meaningful difference between the test and control data. It is important to be able to understand the hypothesis testing, because a lot of interesting functions in R are hypothesis tests. I’ll consider the simple z-test for testing whether the mean of the simple is the same as the hypothesized mean of the population. We’ll see how statistical power, which is the probability of detecting a difference in means, changes with sample size and effect size, which is the size of the difference between the observed sample mean, and the hypothesized population mean. We’ll also see that the significance level \alpha is comparable to the Type-II (false negative) error rate.

Continue reading

Develop Windows Executables from Python Scripts for 32-bit and 64-bit Architecures

In this post I’ll discuss building a Windows executable from a Python script for 32-bit and 64-bit Windows. Producing a 64-bit executable on a 64-bit machine in Windows is easy using PyInstaller, but producing a 32-bit executable on a 64-bit machine takes some tinkering. I ended up setting up a chroot environment on Ubuntu for this task.

Continue reading

Tkinter Optical Character Recognition Training Data Labeler

In this post I’ll demonstrate how to build a object oriented Tkinter GUI application for associating labels to filenames in order to quickly and easily build a set of training data. The Submit button will associate the label with the file, and the Save and Quit button will dump the file and its associated label into a Python dict, and then a cPickle file for later use. This is still a little rough around the edges; it assumes that you’re looking for PNG data in the current directory, and the output overwrites previous output, but it’s a start.

Continue reading