for loop within custom function to create ggplot time series plots

Question

I\'m having a hard time trying to create a function with a for loop that takes the columns in a data frame and creates different plots based on the column name.. I have read

Answer 1

A solution using tidyeval approach similar to this answer which requires ggplot2 v3.0.0

• First we build a function that takes x- & y- columns as inputs. Note the use of rlang::sym, rlang::quo_name & !!.

• Then we can loop through every column using purrr::map.

library(rlang)
library(tidyverse)

philly_df_new <- structure(list(DATE = structure(c(14610, 14611, 14612, 14613, 
    14614, 14615, 14616, 14617, 14618, 14619, 14620, 14621, 14622, 
    14623, 14624, 14625, 14626, 14627, 14628, 14629), class = "Date"), 
        HOURLYDewPointTempC = c(0, -8.9, -15, -12.2, -11.7, -10.6, 
        -8.3, -4.4, -12.2, -17.2, -12.8, -6.1, -10.6, -7.8, -5.6, 
        -2.2, 0.6, 3.9, 0.6, -3.3), HOURLYSeaLevelPressure = c(30, 
        29.79, 29.78, 29.76, 29.81, 29.78, 29.89, 29.87, 29.98, 30.25, 
        30.27, 30.13, 30.22, 30.23, 30.21, 30.23, 30.14, 29.49, 29.95, 
        29.92), DAILYDeptFromNormalAverageTemp = c(-1.7, 2.4, -6.4, 
        -10.3, -6.2, -5.1, -1, -1, -5.9, -10.8, -11.8, -9.7, -3.7, 
        -1.7, -1.6, 4.4, 4.4, 6.4, 8.4, 4.3)), .Names = c("DATE", 
    "HOURLYDewPointTempC", "HOURLYSeaLevelPressure", "DAILYDeptFromNormalAverageTemp"
    ), row.names = c(NA, -20L), class = c("tbl_df", "tbl", "data.frame"
    ))

# define a function that accept strings as input
Plot_Graph <- function(df, x_var, y_var) {

  # convert strings to variable
  x_var <- rlang::sym(x_var)
  y_var <- rlang::sym(y_var)

  # unquote variable using !! 
  ggplot(df, aes(x = !! x_var, y = !! y_var)) + 
    geom_point() + 
    geom_line() +
    labs(x = rlang::quo_name(x_var), y = rlang::quo_name(y_var)) +
    scale_x_date(breaks = scales::pretty_breaks()) +
    theme_classic(base_size = 12)
}

Now loop through every column

plot_list <- colnames(philly_df_new)[-1] %>% 
  map( ~ Plot_Graph(philly_df_new, "DATE", .x))

plot_list
#> [[1]]

#> 
#> [[2]]

#> 
#> [[3]]

# Combine all plots
library(cowplot)

do.call(plot_grid, c(plot_list, 
                     align = "v",
                     axis = 'lr',
                     nrow = 3))

Created on 2018-08-27 by the reprex package (v0.2.0.9000).

Answer 2

The following works.
You were looping along all columns including column "DATE", which is supposed to be the x axis and the loop variable was integer so in the plot's aesthetic y = i was an integer, not a column name.

Note that I call windows() to open a new graphic window. Remove this if not needed.

Plot_Graph <- function(DF, na.rm = TRUE){
  nm = names(DF)[-1]
  for (i in nm) {
    g <- ggplot(DF, aes(x = DATE, y = get(i))) +
            geom_point()
    windows()
    print(g)
  }
}

Plot_Graph(philly_df_new)