Blog Archives

Maximal Information Coefficient (MIC)

December 19, 2011
By
Maximal Information Coefficient (MIC)

Pearson r correlation coefficients for various distributions of paired data (Credit: Denis Boigelot, Wikimedia Commons)A paper published this week in Science outlines a new statistic called the maximal information coefficient (MIC), which is able to equally describe the correlation between paired variables regardless of linear or nonlinear relationship. In...

Read more »

Maximum Covariance Analysis (MCA)

December 13, 2011
By
Maximum Covariance Analysis (MCA)

Maximum Covariance Analysis (MCA) (Mode 1; scaled) of Sea Level Pressure (SLP) and Sea Surface Temperature (SST) monthly anomalies for the region between -180 °W to -70 °W and +30 °N to -30 °S.  MCA coefficients (scaled) are below. The mode represents 94% of the squared covariance fraction (SCF).Maximum Correlation Analysis...

Read more »

Another aspect of speeding up loops in R

November 28, 2011
By
Another aspect of speeding up loops in R

Any frequent reader of R-bloggers will have come across several posts concerning the optimization of code - in particular, the avoidance of loops.Here's another aspect of the same issue. If you have experience programming in other languages besides R, this is probably a no-brainer, but for laymen, like myself, the following example was...

Read more »

Define intermediate color steps for colorRampPalette

November 24, 2011
By
Define intermediate color steps for colorRampPalette

The following function, color.palette(), is a wrapper for colorRampPalette() and allows some increased flexibility in defining the spacing between main color levels. One defines both the main color levels (as with colorRampPalette) and an optional vector containing the number of color levels that should be put in between at equal distances.     The above...

Read more »

Empirical Orthogonal Function (EOF) Analysis for gappy data

November 24, 2011
By
Empirical Orthogonal Function (EOF) Analysis for gappy data

The following is a function for the calculation of Empirical Orthogonal Functions (EOF). For those coming from a more biologically-oriented background and are familiar with Principal Component Analysis (PCA), the methods are similar. In the climate sciences the method is usually used for the decomposition of a data field into dominant spatial-temporal modes. Read...

Read more »

Propagation of error

November 11, 2011
By
Propagation of error

     At the onset, this was strictly an excercise of my own curiosity and I didn't imagine writing this down in any form at all. As someone who has done some modelling work in the past, I'm embarrassed to say that I had never fully grasped how one can gauge the error of a...

Read more »

Converting values to color levels

September 12, 2011
By
Converting values to color levels

     Adding color to a plot is helpful in many situations for visualizing an additional dimension of the data. Again, I wrote the below function "val2col" in R after having coded this manually over and over in the past. It uses similar arguments as the image function in that one defines the...

Read more »

Adding a scale to an image plot

August 31, 2011
By
Adding a scale to an image plot

Here's a function that allows you to add a color scale legend to an image plot (or probably any plot needing a z-level scale). I found myself having to program this over and over again, and just decided to make a plotting function for future use. While I really like the look of levelplot(),...

Read more »

Creating svg graphics for web publishing

July 25, 2011
By

<p><p><p><p><p><p><p><p>This is an error message. If you are reading this, something broke. You may need to upgrade your browser. </p></p></p></p></p></p></p></p> Thanks to the nice post from Revolution Analytics I was finally able to get an svg device working on my Windows OS version of R. It took some additional tips from a fellow user of blogger to...

Read more »

Color reduction of an image – and Warholize?

July 5, 2011
By
Color reduction of an image – and Warholize?

There seems to be several methods out there for reducing the colors in an image. I became interested in this after pondering how this is done in the excellent freeware program IrfanView. Unfortunately, their method is not described anywhere that I coul...

Read more »