Blog Archives

Image color palette replacement

June 9, 2011
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Image color palette replacement

Here is an example of a function I wrote to change the color palette used in an image. The above example comes from a black and white original, although color images can also be used. The function first converts the image to grayscale in order to have ...

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Simulating CMYK mis-registration printing

June 3, 2011
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Simulating CMYK mis-registration printing

I recently came across a poster advertising a children's production of Shakespeare's The Tempest where they purposely used an effect to mimic a mis-registration in CMYK printing. You have probably seen this before as a slight offset in one of t...

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map.xyz(): interpolation of XYZ data and projection onto a map

May 30, 2011
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map.xyz(): interpolation of XYZ data and projection onto a map

     I am still struggling to get a grasp of R's mapping capabilities. Part of my frustration lies in the fact that I often work on areas near the poles, which complicates interpolation across the 180 degree line. For smaller areas, interpolati...

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Array position to matrix coordinates conversion

May 30, 2011
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Array position to matrix coordinates conversion

#A function that is sometimes useful in determining the #coordinate(i.e. row and column number) of a matrix position#(and vice-versa). #Either a vector of positions ("pos") #OR a 2 column matrix of matrix coordinates, ("coord", i.e. cbind(row,col)), #A...

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R functions for Earth geographic coordinate calculations

May 29, 2011
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R functions for Earth geographic coordinate calculations

Here are some functions that I regularly use for geographic data (e.g. binning, filtering, calculation of new positions etc.).#distance in kilometers between two long/lat positions (from "fossil" package)earth.dist <- function (long1, lat1, long2, l...

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