how to make a Pixel picture in R

Question

I have a data.frame as this:

> head(shht)
  tt2 imf           f        a
1   1  c1 0.025735102 461.1430
2   2  c1 0.025735102 336.5967
3   3  c1 0.012977971 334.0539
4   4  c1 0.013013110 303.7454
5   5  c1 0.009130993 301.7031
6   6  c1 0.009153142 287.5305

the data is here

There are a total of four columns. I want to draw a pixmap. The first column is the horizontal axis, the third column is the vertical axis, and the fourth column is the grayscale value.

I tried the following:

> simage=as.image(shht$a,x=cbind(shht$tt2,shht$f))
> image.plot.ts(simage,tt=tt2)
Error in plot.new() : figure margins too large

the image.plot.ts() is a function from EMD. and the as.image() comes from fields.

Answer 1

You could use the image function by generating a matrix of your data?

x = rep(1:5,5)
y = rep(1:5, each = 5)
d = sample(1:10, length(x),replace = T)

df <- data.frame(x = x, y = y, d = d)

mat <- matrix(df[order(df$x, df$y),'d'], 5)
image(mat)

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Or you could make a simple plot of your data, mimicking pixels.

plot(x, y, col=d, pch=15, cex=4)

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edit: I dont fully understand how your data needs to become an image. Since you have only one datapoint per x co-ordinate:

id <- "0B3bNSNFik5wGNGY4VEQ0TFltM3M" 
dat <- read.csv(sprintf("https://docs.google.com/uc?id=%s&export=download", id))

ggplot(dat, aes(x = tt2, y = f, color=a)) + geom_point() + theme_bw()

produces

Answer 2

This is a package for direct manipulation of bitmap images. pixmap It has a range of methods for creating and manipulating them.

One example, directly from the reference manual:

library(pixmap)


x <- seq(-3,3,length=100)
z1 <- outer(x,x,function(x,y) abs(sin(x)*sin(y)))
z2 <- outer(x,x,function(x,y) abs(sin(2*x)*sin(y)))
z3 <- outer(x,x,function(x,y) abs(sin(x)*sin(2*y)))


z <- pixmapRGB(c(z1,z2,z3), 100, 100, bbox=c(-1,-1,1,1))
plot(z, axes=TRUE)