Formatting Decimals in Texts with R

Yihui Xie — Mon, 31 Aug 2009 02:34:24 +0000

Yanping Chen raised a question in the Chinese COS forum on the output of Eviews: how to (re)format the decimal coefficients in equations as text output? For example, we want to round the numbers in CC = 16.5547557654 + 0.0173022117998*PP + 0.216234040485 * PP(-1) + 0.810182697599 * (WP + WG) to the 3rd decimal places. This can be simply done by regular expressions, as decimals always begin with a “.”. The basic steps are:

find out where are the decimals in the character string;
format them;
replace the original decimals with formatted values;

Given a character vector, we can format the decimals with the code below:

# x: equations; FUN: formatting function; ...: passed to FUN
coefFormat = function(x, FUN, ...) {
    sapply(x, function(s) {
        dig = sapply(gregexpr("\\.[0-9]+", s), function(m) {
            sapply(seq(along = m), function(i) {
                substr(s, m[i], m[i] + attr(m, "match.length")[i] - 1)
            })
        })
        for (j in {
            if (is.null(dim(dig)))
                NULL
            else 1:dim(dig)[1]
        }) {
            s = sub(dig[j, 1], substring(FUN(as.numeric(dig[j, 1]), ...),
                2), s, fixed = TRUE)
        }
        s
    })
}

I used sapply() for 3 times to avoid explicit loops but consequently the code might be difficult to read. The critical part is the regular expression “\\.[0-9]+” which means one of more (controlled by “+” after “[0-9]”) digits (“[0-9]” or “[:digit:]”) after a decimal point “.”. As “.” is a metacharacter in regular expressions, we need to use a backslash before it, and again, “\” is a special character in R, so we need another backslash to denote a backslash.

x = readLines(zz <- textConnection(
"CC = 16.5547557654 + 0.0173022117998 * PP + 0.216234040485 * PP(-1) + 0.810182697599 * (WP + WG)

II = 20.2782089394 + 0.150221823899 * PP + 0.61594357734 * PP(-1) - 0.157787636546 * KK

WP = 1.50029688603 + C(10) * XX + 0.146673821502 * XX(-1) + 0.130395687204 * AA
"))
close(zz)

writeLines(coefFormat(x, round, digits = 3))
#  CC = 16.555 + 0.017 * PP + 0.216 * PP(-1) + 0.81 * (WP + WG)
#
#  II = 20.278 + 0.15 * PP + 0.616 * PP(-1) - 0.158 * KK
#
#  WP = 1.5 + C(10) * XX + 0.147 * XX(-1) + 0.13 * AA
#
writeLines(coefFormat(x, formatC, digits = 3, format = "f"))
#  CC = 16.555 + 0.017 * PP + 0.216 * PP(-1) + 0.810 * (WP + WG)
#  
#  II = 20.278 + 0.150 * PP + 0.616 * PP(-1) - 0.158 * KK
#  
#  WP = 1.500 + C(10) * XX + 0.147 * XX(-1) + 0.130 * AA
#

Simulation of Burning Fire in R

Yihui Xie — Fri, 12 Jun 2009 04:43:34 +0000

Linlin Yan posted a cool (hot?) simulation of burning fire with R in the COS forum yesterday, which was indeed a warm welcome. I’m not sure whether our forum members will be scared by the “fire” under the title “Welcome to COS Forum”. The fire was mainly created by the function image() with carefully designed rows and columns in heated colors heat.colors(). Here is one of the pictures generated from his code:

Simulation of Burning Fire in R

And code here:

Fire <- function(row = 100, col = 100, time = 500, fade = 0.03) {
  fire <- matrix(0, col, row);
  fire[,1] <- runif(col);

  for (t in 1:time) {
    image(fire, col = rev(heat.colors(row)),
      axes = FALSE, main = "Welcome to COS Forum!");

    fire <- (
      fire +
      cbind(fire[,1], fire[c(col,1:(col-1)), 1:(row - 1)]) +
      cbind(fire[,1], fire[                , 1:(row - 1)]) +
      cbind(fire[,1], fire[c(2:col,1)      , 1:(row - 1)])
      ) / 4;
    fire <- cbind(fire[,1], (fire + fade / 5 - runif(1, max = fade))[,-1]);
    fire[fire < 0] <- 0;

    r <- runif(1);
    if (r < .1) fire[,1] <- fire[,1][c(2:col, 1)];
    if (r > .9) fire[,1] <- fire[,1][c(col, 1:(col-1))];
  };
  NULL;
}

The speed of drawing animation frames is rather slow in my computer, but it doesn’t matter since we can use the animation package (hey, you are advertising!) to save all the image frames and convert them to a single animation file.

library(animation)
# set row=50 instead of the default 100 to let the fire burn to the ceiling
# make sure you have installed the SWF Tools and the command 'png2swf' can
#    be executed (with or w/o it installation path); see ?saveSWF
saveSWF(Fire(50), interval = 0.05, dev = "png", outdir = getwd(),
    para = list(mar = c(0, 0, 2, 0)))

Now the animation is much more smooth than what we saw in R graphics window.

Thanks, awesome Linlin.

For those who are not familiar with the website “Capital of Statistics” (COS), I’d like to give a brief introduction here: this website was built 3 years ago by me and it was originally a Chinese website for discussion in statistics, but later I thought a place for English-speaking visitors was also necessary, so an English forum was constructed: http://cos.name/en/. Please feel free to join us if you are interested.

Statistics, R, Graphics and Fun » Capital of Statistics

Formatting Decimals in Texts with R

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Simulation of Burning Fire in R

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