datagrid - R tableGrob heatmap or conditional formating in column

Question

Is there a way to create a similar effect to excel's conditional formating -> color scales in order to present a table in grid.table/tablegrob object? The color indicator should be red for the lower values and green for the higher values in the column. That object format is needed so the table can be presented in grid format along with plots.

Thank you.

Answer 1

You can do this within tableGrob. You create a vector of colours, and then assign these to the cells.

So using the data from clemens's answer:

library(gridExtra)
library(grid)

# define colour vector
# change `vec` argument of `findInterval` to suit your cut-points
cols <- c("red" ,"orange", "green") [findInterval(my_data$Balance, c(-Inf, 1e4, 2e4, Inf))]
# or 
# https://stackoverflow.com/questions/34517031/red-amber-green-sequential-palette-for-treemap-in-r
cols <- colorRampPalette(c("red", "yellow", "green"))(nrow(my_data))[rank(my_data$Balance)]


# create tales individually for each column
# this make it easy to assign colours to rows
t1 <- tableGrob(my_data["Balance"], 
               theme=ttheme_default(
                      core=list(bg_params = list(fill=cols)),
                      colhead = list(bg_params=list(fill="white", col="grey90"))), 
                      rows = NULL)
t2 <- tableGrob(my_data["ID"], 
               theme=ttheme_default(
                      core=list(bg_params = list(fill="white", col="grey90")),
                      colhead = list(bg_params=list(fill="white", col="grey90"))),
                      rows = NULL)

# join tables
tab <- gtable_combine(t2, t1)
# grid.newpage() ; grid.draw(tab)



# if also want to add black border
# https://stackoverflow.com/questions/31506294/gtable-put-a-black-line-around-all-cells-in-the-table-body
library(gtable)
tab <- gtable::gtable_add_grob(tab, 
                             grobs = rectGrob(gp=gpar(fill=NA, lwd=2)), 
                             t = 1, b = nrow(tab), l = 1, r = ncol(tab))

grid.newpage() ; grid.draw(tab)