Blog Archives

A small neuroimage interactive plotter

April 9, 2015
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A small neuroimage interactive plotter

Manipulate Package The manipulate from RStudio allows you to create simple Tcl/Tk operators for interactive visualization. I will use it for a simple slider to view different slices of an image. fslr package I'm calling the fslr package because I know that if you have it installed, you will likely have FSL and have a

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matlabr: a Package to Calling MATLAB from R with system

April 8, 2015
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matlabr: a Package to Calling MATLAB from R with system

In my research, I primarily use R, but I try to use existing code if available. In neuroimaging and other areas, that means calling MATLAB code. There are some existing solutions for the problem of R to MATLAB: namely the R.matlab package and the RMatlab package (which can call R from MATLAB as well). I

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White Matter Segmentation in R

April 7, 2015
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White Matter Segmentation in R

Goals and Overall Approach We will use multiple packages and pieces of software for white matter (and gray matter/cerebro spinal fluid (CSF)) segmentation. The overall approach will be, with the required packages in parentheses: N4 Inhomogeneity Bias-Field Correction (extrantsr and ANTsR) Brain extraction using BET and additional tools (extrantsr and fslr) FAST for tissue-class segmentation.

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The Unofficial ENAR 2015 Itinerary Maker

March 10, 2015
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The Unofficial ENAR 2015 Itinerary Maker

It’s almost ENAR 2015! The final program is out with all the sessions. The last conference I went to, the International Stroke Conference, had a program planner hosted by abstracts online. Although there are parts of this system I would like to change, I believe it is helpful for looking up sessions, presenters, and especially

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Using Tables for Statistics on Large Vectors

March 1, 2015
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Using Tables for Statistics on Large Vectors

This is the first post I’ve written in a while. I have been somewhat radio silent on social media, but I’m jumping back in. Now, I work with brain images, which can have millions of elements (referred to as voxels). Many of these elements are zero (for background). We want to calculate basic statistics on

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The average Stripe employee! Congrats to Alyssa!

January 2, 2015
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The average Stripe employee! Congrats to Alyssa!

Recently, my colleague and fellow blogger Alyssa Frazee accepted a job at Stripe. All of us at JHU Biostat are happy for her, yet sad to see her go. While perusing Stripe’s website, I found the About page, where each employee has a photo of themselves. I’ve been playing around with some PCA and decompositions,

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Adding Cost Functions to ROCR performance objects

December 22, 2014
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Adding Cost Functions to ROCR performance objects

In my last post, I gave an introduction of the ROCR package and how to use it for ROC analysis. In the ROCR reference manual, it states “new performance measures can be added using a standard interface”, but I have not found that to be so. I may have missed some crucial step, but others

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A small introduction to the ROCR package

December 19, 2014
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A small introduction to the ROCR package

I've been doing some classification with logistic regression in brain imaging recently. I have been using the ROCR package, which is helpful at estimating performance measures and plotting these measures over a range of cutoffs. The prediction and performance functions are the workhorses of most of the analyses in ROCR I've been doing. For those

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My Commonly Done ggplot2 graphs: Part 2

December 18, 2014
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My Commonly Done ggplot2 graphs: Part 2

In my last post I described some of my commonly done ggplot2 graphs. It seems as though some people are interested in these, so I was going to follow this up with other plots I make frequently. Scatterplot colored by continuous variable The setup of the data for the scatterplots will be the same as

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My Commonly Done ggplot2 graphs

October 30, 2014
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My Commonly Done ggplot2 graphs

In my last post, I discussed how ggplot2 is not always the answer to the question “How should I plot this” and that base graphics were still very useful. Why Do I use ggplot2 then? The overall question still remains: why (do I) use ggplot2? ggplot2 vs lattice For one, ggplot2 replaced the lattice package

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