This guide presents a toolkit for writing research papers and monographs using Emacs, Org-mode and R. Org-mode allows embedding statistical code in the document to generate results that can be revised and reproduced, integration of bibliographic references with a database, and consistent formatting without any manual tweaking using excellent support ... [Read more...]

AQUASTAT, developed and maintained by the Food and Agriculture Organization of the UN, is the global database that gives quantitative information on water resources and withdrawal of water for different uses. Agricultural water withdrawal is defined as follows: Annual quantity of self-supplied water withdrawn for irrigation, livestock and aquaculture purposes. ... [Read more...]

I recently had to prepare a beamer presentation in hindi/devanagari. I usually use emacs-orgmode  with a lot of R source code embedded in it to prepare my beamer presentations. To adapt the entire setup to work with devanagari, this is what I needed to do.      Make orgmode export to ... [Read more...]

I discovered a new, very useful, R function yesterday: ave. This is what it does: “Subsets of ‘x[]‘ are averaged, where each subset consist of those observations with the same factor levels.” But interestingly, you can use any function other than average. The output of that function is set against ... [Read more...]

If a model is estimated using the following code: lm(y~x1+x2)-__p 1. bptest(p) does the Breuch Pagan test to formally check presence of heteroscedasticity. To use bptest, you will have to call lmtest library. 2. If the test is positive (low p value), you should see if ... [Read more...]

sapply(a,class) gives type of field (character, numeric, or factor) for each variable in the data frame a. [Read more...]

?rollmean (package=zoo)?rollmedian (package=zoo)?runmed (package=stats) [Read more...]

?relevel : The levels of a factor are re-ordered so that the level specified by ‘ref’ is first and the others are moved down. This is useful for ‘contr.treatment’ contrasts which take the first level as the reference. [Read more...]

In my previous post on this issue, I had presented a code that made weighted boxplots and annotated them with boxplot statistics and the mean values. The problem with that code was that it printed these annotations right on the vertical axes of the boxplots. Also, a relatively minor problem ... [Read more...]

Here are some useful tips on the issue. V. [Read more...]

Some of the Census 2001 data are in microsoft access files (having filename extensions .mdb). A microsoft access file can have several tables inside, each of which contains data. There is a software called mdbtools that can be used to read access files. The command mdb-tables can be used to see ... [Read more...]

John Verzani’s book has a title page that shows a scatterplot with histograms of x and y variables along the two axes. It is a very powerful way of looking at two distributions. The plot was generated through a function simple.scatterplot. The function is made available as part ... [Read more...]

R News 2(2) has papers on grid and lattice packages. R News 3(2) has papers on base, grid and gridBase. Essential stuff for anybody trying to master R graphics V. [Read more...]

Hadley Wickham’s ggplot is a very interesting package. It makes beautiful graphics, integrates well with some of the other packages to allow you to superimpose the plots of various types of estimates on plots of data. In particular, it uses colours very well. The default colour schemes are aesthetically ... [Read more...]

Use “select=c(var1,var2)” in the subset command to select var1 and var2. Use “select=-c(var1,var2)” in the subset command to drop var1 and var2. Technorati Tags: GNU-R [Read more...]

A commonly reported problem with ps2pdf is that it does not always guess the page orientation right. A neat solution is here http://allendowney.com/essays/orientation/ I just edited the gs_statd.ps to define the wide page and added an alias in my bashrc called widepdf to ... [Read more...]

Here is an interesting document on problems of using Microsoft Excel for statistical analysis. http://gcrc.ucsd.edu/biostatistics/Excel.pdf Technorati Tags: statistics, excel, microsoft [Read more...]