Change colors according to the coefficient calculated by the geom_smooth

Hi,
I have data that for each group I need to plot a line (geom_smooth) based on values from two variables.
However, since I have 29 groups, I want to plot the ones with a positive slope in a color and the ones with a negative slope in another color.
Below, data simulates the data a have with only two groups (A and B) with opposite perfect correlations. In this case, the graph should display two lines of different colors.

data<-data.frame(var1 = c(rep(seq(1,30),2)),
var2= c(seq(30,1),seq(1,30)),
group=c(rep("A",30),rep("B",30)))

I do not know a way to access the fit results within geom_smooth. I used the lm() function to do the fit beforehand and stored the slope coefficient in the original data frame. It is then easy to color the fit line according to slope.

library(ggplot2)
library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
DF <- data.frame(var1 = c(rep(seq(1,30),2)),
                 var2= c(seq(30,1),seq(1,30)),
                 grp=c(rep("A",30),rep("B",30)))

FitFunc <- function(x1, x2) {
  coef(lm(x2 ~ x1))[2]
}
Stat <- DF %>% group_by(grp) %>% summarize(FIT = FitFunc(.data$var1, .data$var2))
DF <- DF %>% inner_join(Stat, by = "grp")

ggplot(DF, aes(var1, var2, group = grp, color = FIT)) + geom_point() +
  geom_smooth(method = "lm", se = FALSE )

Created on 2020-03-22 by the reprex package (v0.3.0)

1 Like

Hi, and welcome!

Please see the FAQ: What's a reproducible example (`reprex`) and how do I do one? Using a reprex, complete with representative data will attract quicker and more answers. You've done the equivalent here, but with more involved data it's a great way to catch syntax errors.

As a preface, data is a function name. I like to avoid using it as the name of a user created object. When in doubt, just

data
#> function (..., list = character(), package = NULL, lib.loc = NULL, 
#>     verbose = getOption("verbose"), envir = .GlobalEnv, overwrite = TRUE) 
#> {
#>     fileExt <- function(x) {
#>         db <- grepl("\\.[^.]+\\.(gz|bz2|xz)$", x)
#>         ans <- sub(".*\\.", "", x)
#>         ans[db] <- sub(".*\\.([^.]+\\.)(gz|bz2|xz)$", "\\1\\2", 
#>             x[db])
#>         ans
#>     }
#>     names <- c(as.character(substitute(list(...))[-1L]), list)
#>     if (!is.null(package)) {
#>         if (!is.character(package)) 
#>             stop("'package' must be a character string or NULL")
#>         if (any(package %in% "base")) 
#>             warning("datasets have been moved from package 'base' to package 'datasets'")
#>         if (any(package %in% "stats")) 
#>             warning("datasets have been moved from package 'stats' to package 'datasets'")
#>         package[package %in% c("base", "stats")] <- "datasets"
#>     }
#>     paths <- find.package(package, lib.loc, verbose = verbose)
#>     if (is.null(lib.loc)) 
#>         paths <- c(path.package(package, TRUE), if (!length(package)) getwd(), 
#>             paths)
#>     paths <- unique(normalizePath(paths[file.exists(paths)]))
#>     paths <- paths[dir.exists(file.path(paths, "data"))]
#>     dataExts <- tools:::.make_file_exts("data")
#>     if (length(names) == 0L) {
#>         db <- matrix(character(), nrow = 0L, ncol = 4L)
#>         for (path in paths) {
#>             entries <- NULL
#>             packageName <- if (file_test("-f", file.path(path, 
#>                 "DESCRIPTION"))) 
#>                 basename(path)
#>             else "."
#>             if (file_test("-f", INDEX <- file.path(path, "Meta", 
#>                 "data.rds"))) {
#>                 entries <- readRDS(INDEX)
#>             }
#>             else {
#>                 dataDir <- file.path(path, "data")
#>                 entries <- tools::list_files_with_type(dataDir, 
#>                   "data")
#>                 if (length(entries)) {
#>                   entries <- unique(tools::file_path_sans_ext(basename(entries)))
#>                   entries <- cbind(entries, "")
#>                 }
#>             }
#>             if (NROW(entries)) {
#>                 if (is.matrix(entries) && ncol(entries) == 2L) 
#>                   db <- rbind(db, cbind(packageName, dirname(path), 
#>                     entries))
#>                 else warning(gettextf("data index for package %s is invalid and will be ignored", 
#>                   sQuote(packageName)), domain = NA, call. = FALSE)
#>             }
#>         }
#>         colnames(db) <- c("Package", "LibPath", "Item", "Title")
#>         footer <- if (missing(package)) 
#>             paste0("Use ", sQuote(paste("data(package =", ".packages(all.available = TRUE))")), 
#>                 "\n", "to list the data sets in all *available* packages.")
#>         else NULL
#>         y <- list(title = "Data sets", header = NULL, results = db, 
#>             footer = footer)
#>         class(y) <- "packageIQR"
#>         return(y)
#>     }
#>     paths <- file.path(paths, "data")
#>     for (name in names) {
#>         found <- FALSE
#>         for (p in paths) {
#>             tmp_env <- if (overwrite) 
#>                 envir
#>             else new.env()
#>             if (file_test("-f", file.path(p, "Rdata.rds"))) {
#>                 rds <- readRDS(file.path(p, "Rdata.rds"))
#>                 if (name %in% names(rds)) {
#>                   found <- TRUE
#>                   if (verbose) 
#>                     message(sprintf("name=%s:\t found in Rdata.rds", 
#>                       name), domain = NA)
#>                   thispkg <- sub(".*/([^/]*)/data$", "\\1", p)
#>                   thispkg <- sub("_.*$", "", thispkg)
#>                   thispkg <- paste0("package:", thispkg)
#>                   objs <- rds[[name]]
#>                   lazyLoad(file.path(p, "Rdata"), envir = tmp_env, 
#>                     filter = function(x) x %in% objs)
#>                   break
#>                 }
#>                 else if (verbose) 
#>                   message(sprintf("name=%s:\t NOT found in names() of Rdata.rds, i.e.,\n\t%s\n", 
#>                     name, paste(names(rds), collapse = ",")), 
#>                     domain = NA)
#>             }
#>             if (file_test("-f", file.path(p, "Rdata.zip"))) {
#>                 warning("zipped data found for package ", sQuote(basename(dirname(p))), 
#>                   ".\nThat is defunct, so please re-install the package.", 
#>                   domain = NA)
#>                 if (file_test("-f", fp <- file.path(p, "filelist"))) 
#>                   files <- file.path(p, scan(fp, what = "", quiet = TRUE))
#>                 else {
#>                   warning(gettextf("file 'filelist' is missing for directory %s", 
#>                     sQuote(p)), domain = NA)
#>                   next
#>                 }
#>             }
#>             else {
#>                 files <- list.files(p, full.names = TRUE)
#>             }
#>             files <- files[grep(name, files, fixed = TRUE)]
#>             if (length(files) > 1L) {
#>                 o <- match(fileExt(files), dataExts, nomatch = 100L)
#>                 paths0 <- dirname(files)
#>                 paths0 <- factor(paths0, levels = unique(paths0))
#>                 files <- files[order(paths0, o)]
#>             }
#>             if (length(files)) {
#>                 for (file in files) {
#>                   if (verbose) 
#>                     message("name=", name, ":\t file= ...", .Platform$file.sep, 
#>                       basename(file), "::\t", appendLF = FALSE, 
#>                       domain = NA)
#>                   ext <- fileExt(file)
#>                   if (basename(file) != paste0(name, ".", ext)) 
#>                     found <- FALSE
#>                   else {
#>                     found <- TRUE
#>                     zfile <- file
#>                     zipname <- file.path(dirname(file), "Rdata.zip")
#>                     if (file.exists(zipname)) {
#>                       Rdatadir <- tempfile("Rdata")
#>                       dir.create(Rdatadir, showWarnings = FALSE)
#>                       topic <- basename(file)
#>                       rc <- .External(C_unzip, zipname, topic, 
#>                         Rdatadir, FALSE, TRUE, FALSE, FALSE)
#>                       if (rc == 0L) 
#>                         zfile <- file.path(Rdatadir, topic)
#>                     }
#>                     if (zfile != file) 
#>                       on.exit(unlink(zfile))
#>                     switch(ext, R = , r = {
#>                       library("utils")
#>                       sys.source(zfile, chdir = TRUE, envir = tmp_env)
#>                     }, RData = , rdata = , rda = load(zfile, 
#>                       envir = tmp_env), TXT = , txt = , tab = , 
#>                       tab.gz = , tab.bz2 = , tab.xz = , txt.gz = , 
#>                       txt.bz2 = , txt.xz = assign(name, read.table(zfile, 
#>                         header = TRUE, as.is = FALSE), envir = tmp_env), 
#>                       CSV = , csv = , csv.gz = , csv.bz2 = , 
#>                       csv.xz = assign(name, read.table(zfile, 
#>                         header = TRUE, sep = ";", as.is = FALSE), 
#>                         envir = tmp_env), found <- FALSE)
#>                   }
#>                   if (found) 
#>                     break
#>                 }
#>                 if (verbose) 
#>                   message(if (!found) 
#>                     "*NOT* ", "found", domain = NA)
#>             }
#>             if (found) 
#>                 break
#>         }
#>         if (!found) {
#>             warning(gettextf("data set %s not found", sQuote(name)), 
#>                 domain = NA)
#>         }
#>         else if (!overwrite) {
#>             for (o in ls(envir = tmp_env, all.names = TRUE)) {
#>                 if (exists(o, envir = envir, inherits = FALSE)) 
#>                   warning(gettextf("an object named %s already exists and will not be overwritten", 
#>                     sQuote(o)))
#>                 else assign(o, get(o, envir = tmp_env, inherits = FALSE), 
#>                   envir = envir)
#>             }
#>             rm(tmp_env)
#>         }
#>     }
#>     invisible(names)
#> }
#> <bytecode: 0x7faa96e96398>
#> <environment: namespace:utils>

Created on 2020-03-22 by the reprex package (v0.3.0)

for any name you're thinking of using. You can also do things like data_.

suppressPackageStartupMessages(library(ggplot2)) 

# the sample data
dat_ <-data.frame(var1 = c(rep(seq(1,30),2)),
var2= c(seq(30,1),seq(1,30)),
group=c(rep("A",30),rep("B",30)))

# create the base layer

p <- ggplot(dat_,aes(var1,var2, colour = group))

# add lines
p + geom_line()

Created on 2020-03-22 by the reprex package (v0.3.0)

Thank you. It works!

This topic was automatically closed 7 days after the last reply. New replies are no longer allowed.