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Tag: programming

Some good Python Blogs and Resources

Erik Marsja Erik Marsja
December 7, 2015
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Some good Python Blogs and ResourcesPython for Data Analysis

In this post you will find some really good Python Blogs and Resources. Most of these really helped me when moving from proprietary software to free and Open Source software (e.g., PsychoPy written in Python).  The links are divided into two categories: general and research. In the ‘general’ category you will find good Python resources that might be more general and introducing. That is, more helpful for general problems and you might want to start here. In the ‘research’ category there are links to good Python resources that are more specific to use in research (e.g., PsychoPy and data analysis). The links in the ‘research’ category mainly contains links to Python blogs.

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Reverse scoring using R statistical environment

Erik Marsja Erik Marsja
December 4, 2015
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Reverse scoring using R statistical environmentReverse scoring using R

This post is my first on R and it will describe a method to reverse scores using R.

Reverse scoring

In many instruments (i.e., questionnaires) some items are phrased so that a strong agreement indicates something negative (e.g., “When there is music in the room I find it hard to concentrate on reading”). For more information on reverse scoring, please see my earlier post: Reverse scoring in Python.  Since I was more  familiar with Python  compared to R, and I had no a clue on how to do this in SPSS, I wrote a Python script. The Python script used a function that used Pandas DataFrame and it reversed the scores nice and quickly.

However, in R was pretty much as simple to do reverse scoring as in Python. In the following script a data frame is generated with column names (i.e., columnNames,’Q1′ to ‘Q6’) and some data is generated using replicate and sample (100 responses, on the 6 questions). After that you will find two methods, that are pretty much the same, for reversing the can be found. The methods only differ in how the columns are selected. The first are select based on the index of the column and the second select based on the column names to be reversed (might be preferable if you know the names of columns but not the indices).

R Script

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Free & Useful Software – PsychoPy

Erik Marsja Erik Marsja
November 29, 2015
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PsychoPy

This post will describe why I prefer using PsychoPy before other software. When I started getting involved in research (i.e., when doing my Bachelor’s and Masters theses) I used the software that was accessible for me. That is, some of the most commonly used software at the department I was studying at. After starting my Ph.D. studies I got more and more annoyed with one of the software we used to build experimental tasks  in (i.e., E-prime).

First, I was not familiar with the scripting language (called ‘e-basic’) that was needed, for instance use, to solve pseudo-randomization, and for sending signals to a specially built device I was going to use in my experiments. Second, I prefer to use Linux systems and e-prime is limited to Windows. In fact, e-prime seemed to be working best Windows Vista or earlier but our lab computers were, and are, running Windows 7 (might have changed since back then). Some time into my Ph.D. studies I found PsychoPy which is written in Python, a programming language that I did know, and it seemed like a good alternative to e-prime, and other similar software, to create experiments in.

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Collecting data with Scrapy

Erik Marsja Erik Marsja
November 2, 2015
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This rather long (counting the Python code) tutorial assumes that you are interested in scraping data off the web using Scrapy. It might also be limited to Linux.

Scrapy can be installed using pip:

To create a new Scrapy project open up a terminal and create a directory where you will store your Scrapy projects and change do that directory and run this (change ‘psysci’ to whatever your project will be named):

 

Item

We start with the Item class and create an object to store our scraped data in. In my example I scrape the article title, type of article, the articles abstract, when the article was received and when it got accepted for publication, which year it was publicized (and month) and the articles keywords.

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Reverse Scoring in Python

Erik Marsja Erik Marsja
July 14, 2015
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When working with questionnaires that use a Likert scale (e.g., strongly disagree, disagree, neutral, agree, strongly agree) we sometimes want to reverse the scoring.  For instance, in a questionnaire subjective experiences of cognition some of the questions can be positively worded (e.g., “I find it easy to read while talking in the telephone at the same time”). However, we often have questions that are negatively worded (e.g., “When there is music in the room I find it hard to concentrate on reading”).

In the case of positively worded questions we can score them like this; strongly disagree with a score of 1, disagree= 2, neutral =3, agree = 4 and strongly disagree =5. However, the same scoring can’t be applied for the negatively worded questions. We now need to reverse the score of these questions.  In the python example below, score 5 becomes 1, 4 becomes 2, 2 becomes 4 and 1 becomes 5. Three, on the other hand, (neutral) stays the same.

The following Python example uses Pandas DataFrame. If you need to learn more about Pandas check out my dataframe tutorial.

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Python script for trial randomization

Erik Marsja Erik Marsja
October 9, 2014
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In this post you will find a Python script for randomizing conditions with constraints (i.e., never 2 consecutive trials of X). This script will in a later post be implemented in a cross-modal oddball task created in Psychopy.

I recently started to use Psychopy to build experiments. To build my experiments (mainly oddball tasks) I have, up until I found psychopy, used e-prime. In an oddball task one does not usually present several oddball (typically called “novel” or “deviant”) stimuli in succession. Without getting into detail; I was not able to solve this problem with e-primes scripting language “e-basic” so I made a python script instead. With this script I pre-generated .txt-files that I loaded into e-prime and got my constraints fulfilled.

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