How to plot filtered data with loop in R and combine them with facet_grid?

Question

I am new in R, so my question could seem very trivial for someone, but I need a solution. I have a data frame:

`structure(list(Time = c(0, 0, 0), Node = 1:3, Depth = c(0, -10, 
-20), Head = c(-1000, -1000, -1000), Moisture = c(0.166, 0.166, 
0.166), HeadF = c(-1000, -1000, -1000), MoistureF = c(0.004983, 
0.004983, 0.004983), Flux = c(-0.00133, -0.00133, -0.00133), 
    FluxF = c(-0.00122, -0.00122, -0.00122), Sink = c(0, 0, 0
    ), Transf = c(0, 0, 0), TranS = c(0, 0, 0), Temp = c(20, 
    20, 20), ConcF = c(0, 0, 0), ConcM = c(0, 0, 0)), row.names = c(NA, 
3L), class = "data.frame")`.

I am able to plot a single TranS vs Time Single plot, where color = Transf (using scale_color_viridis). I want to create plots with a filtered data for( depth = -20, depth = -40 , -60, -80 and -100) Note: that title also have to be changed according to a depth value. These plots then I want to put next to each other using facet_grid.

I have tried in a such way:

plot_d20 <-plot_node %>% filter(plot_node$Depth == -20)
plot_d40 <-plot_node %>% filter(plot_node$Depth == -40)
plot_d60 <-plot_node %>% filter(plot_node$Depth == -60)
plot_d80 <-plot_node %>% filter(plot_node$Depth == -80)
plot_d100 <-plot_node %>% filter(plot_node$Depth == -100)

depth_plot <- c(plot_d20,plot_d40,plot_d60,plot_d80,plot_d100)

for (p in depth_plot){
ggpS<-ggplot(p, aes(Time, TranS, color=Transf) ) + 
  geom_point(alpha = 1)+
  scale_color_viridis(option = "D")+
  scale_x_continuous(limits = c(0,1400), breaks = seq(0,1400,200))+
  ggtitle('Solute Mass Transfer for depth = 20mm')
ggpS
}

But it doesn't work. R says: data must be a data frame, or another object coercible by fortify(), not a numeric vector. And I don't know how to make my title dynamic and combine it with facet_grid or on a single plot, but in this case, I will face difficulty to distinguish the lines and assigning the legend to the plot by color, because color already represents another variable. What is the possible way to accomplish that?

Answer 1

Edit: Understand the question differently.

facet_grid accepts a single data.frame, and uses one of that frames values to split a chart into multiple subplots. Your question describes combining multiples charts into a single chart, which is available as a function from the cowplot library. However, If you are interested in faceting the data, here is a way to filter and facet_wrap.

Example with Iris data:

library(tidyverse)
iris %>% 
  filter(Sepal.Length %in% c(6.4,5.7,6.7,5.1,6.3,5)) %>%  ### Your values here
  ggplot(aes(Petal.Length, Petal.Width, color=Species)) + 
  geom_point(alpha = 1) +
  scale_color_viridis_d()+ #(option = "D") + ### New function name
  #scale_x_continuous(limits = c(0,1400), breaks = seq(0,1400,200))+
  facet_wrap("Sepal.Length") +
  # facet_grid("Sepal.Length") + ### Alternative Layout
  ggtitle('Sepal Length Range')

Answer 2

To create a "grid" of plots with only one faceting variable, you'll actually want to use facet_wrap(). You can create your facet titles before plotting, and change the formatting of strip.text within theme() to make them look more "title-like."

library(dplyr)
library(ggplot2)

plot_node %>% 
  mutate(
    facet = paste0("Solute Mass Transfer for Depth = ", abs(Depth), "mm")
  ) %>% 
  ggplot(aes(Time, TranS, color=Transf)) + 
  geom_point(alpha = 1) +
  scale_color_viridis_c(option = "D") +
  scale_x_continuous(limits = c(0, 1400), breaks = seq(0, 1400, 200)) +
  facet_wrap(vars(facet), ncol = 2, scales = "free") +
  theme_minimal() + 
  theme(strip.text = element_text(size = 12, face = "bold"))