How to formatting numbers by column in a table (tableGrob)

Question

I have been trying to learn how to format tables for output in R. I'm now trying to take the table in example and format the numbers in the columns. I would like to have two digits in some columns and none in some columns like the rank column. Also, I would like to keep the row names as Year Month. How would one go about creating a table like this?

Note: Also the "3" in the column 'sepal.with' is printed as "3" not "3.0".

library(gtable)
library(grid)
library(gridExtra)
library(zoo)

iris <- as.matrix(iris[1:4, 1:3])
rownames(iris)<-as.yearmon(seq(as.Date("2000/1/1"), as.Date("2000/4/1"), by = "month"))
RankColumn<-seq(1, 4, by = 1)
iris<-cbind(iris, RankColumn)
iris<- round(as.matrix(iris), digits=2)


# a simple function to scale each column to the range [0, 1]
norm <- function(x) {
apply(x, 2, function(y){(y-min(y))/(max(y)-min(y))})
}

bluecol <- colorRamp(c("#3366EE", "#AABBFF", "#DDDDFF"))(norm(iris))
bluecol <- rgb(bluecol[, 1], bluecol[, 2], bluecol[, 3], max=255)

tt <- ttheme_default(core=list(bg_params=list(fill=bluecol)))

g <- tableGrob(iris, theme=tt)
g <- gtable_add_grob(g,
grobs = rectGrob(gp = gpar(fill = NA, lwd = 2)),
t = 2, b = nrow(g), l = 1, r = ncol(g))
g <- gtable_add_grob(g,
grobs = rectGrob(gp = gpar(fill = NA, lwd = 2)),
t = 1, l = 1, r = ncol(g))
grid.draw(g)

Answer 1

While functional and flexible, I found Matt's format function a bit over complicated. A little sprintf magic should suffice. Also, converting the yearmon objects to character will keep the format.

library(gtable)
library(grid)
library(gridExtra)
library(zoo)

data(iris)
iris <- iris[1:4, 1:3]
rownames(iris) <- as.character(as.yearmon(
  seq(as.Date("2000/1/1"), as.Date("2000/4/1"), by = "month")))
iris$RankColumn <- 1:nrow(iris)

# a simple function to scale each row or column to the range [0, 1]
# will convert characters to numerics if in a sensible format
norm <- function(x, mar=2) {
    rnames <- rownames(x)
    x <- apply(x, 2, as.numeric)
    x <- apply(x, mar, function(y){(y-min(y))/(max(y)-min(y))})
    rownames(x) <- rnames
    x
}

# function to pad with zero
# by default does not pad integers
zeropad <- function(x, nz=1, exc.int=TRUE) {
    if (is.integer(x) & exc.int) {
        x
    } else { 
        sprintf(paste0("%.", nz, "f"), x)
    }
}

bluecol <- colorRamp(c("#3366EE", "#AABBFF", "#DDDDFF"))(norm(iris))
bluecol <- rgb(bluecol[, 1], bluecol[, 2], bluecol[, 3], max=255)

tt <- ttheme_default(core=list(bg_params=list(fill=bluecol)))

# convert floats to zero-padded characters
iris[1:ncol(iris)] <- sapply(iris, zeropad, 2)

g <- tableGrob(iris, theme=tt)
g <- gtable_add_grob(g,
                     grobs = rectGrob(gp = gpar(fill = NA, lwd = 2)),
                     t = 2, b = nrow(g), l = 1, r = ncol(g))
g <- gtable_add_grob(g,
                     grobs = rectGrob(gp = gpar(fill = NA, lwd = 2)),
                     t = 1, l = 1, r = ncol(g))
plot.new()
grid.draw(g)

(edited to work exclusively with data frames. norm and zeropad made a bit 'smarter')

Answer 2

Something like this may work to get you the format you're looking for.

library(gtable)
library(grid)
library(gridExtra)
library(zoo)

iris <- as.matrix(iris[1:4, 1:3])
rownames(iris)<-as.yearmon(seq(as.Date("2000/1/1"), as.Date("2000/4/1"), by = "month"))
RankColumn<-seq(1, 4, by = 1)
iris<-cbind(iris, RankColumn)

# Create the matrix
iris<- as.matrix(iris)


# a simple function to scale each column to the range [0, 1]
norm <- function(x) {
  apply(x, 2, function(y){(y-min(y))/(max(y)-min(y))})
}

# function to format columns
format.column <- function(matrix, colnum, rounding, decimals){
  formatted <- format(round(as.numeric(matrix[,colnum]), digits = rounding),nsmall = decimals)
  return(formatted)
}

bluecol <- colorRamp(c("#3366EE", "#AABBFF", "#DDDDFF"))(norm(iris))
bluecol <- rgb(bluecol[, 1], bluecol[, 2], bluecol[, 3], max=255)

tt <- ttheme_default(core=list(bg_params=list(fill=bluecol)))

# Set formatting for individual columns 
# Adjust these or add additional columns to format as necessary
iris[,1] <- format.column(matrix = iris, colnum = 1, rounding = 2, decimals = 2)
iris[,2] <- format.column(matrix = iris, colnum = 2, rounding = 2, decimals = 1)

g <- tableGrob(iris, theme=tt)
g <- gtable_add_grob(g,
                     grobs = rectGrob(gp = gpar(fill = NA, lwd = 2)),
                     t = 2, b = nrow(g), l = 1, r = ncol(g))
g <- gtable_add_grob(g,
                     grobs = rectGrob(gp = gpar(fill = NA, lwd = 2)),
                     t = 1, l = 1, r = ncol(g))
grid.draw(g)