Write a function to plot original value, mom and yoy change for time series data in 3 subplots

Question

Given two monthly time series data sample from this link.

I have used code below to create one plot containing 3 subplots: plot1 for the original values, plot2 for month over month changes, and plot3 for year over year changes.

library(xlsx)
library(ggplot2)
library(reshape)
library(dplyr)
library(tidyverse)
library(lubridate)
library(cowplot)
library(patchwork)

df <- read.xlsx('./sample_data.xlsx', 'Sheet1')
colnames(df)
# df

cols <- c('food_index', 'energy_index')

df <- df %>% mutate(date=as.Date(date)) %>% 
  mutate(across(-contains('date'), as.numeric)) %>% 
  mutate(date= floor_date(date, 'month')) %>%
  group_by(date) %>%
  summarise_at(vars(cols), funs(mean(., na.rm=TRUE))) %>%
  mutate(across(cols, list(yoy = ~(. - lag(., 12))/lag(., 12)))*100) %>%
  mutate(across(cols, list(mom = ~(. - lag(., 1))/lag(., 1)))*100) %>% 
  filter(date >= '2018-01-01' & date <= '2021-12-31') %>%
  as.data.frame()

df1 <- df %>%
  select(!grep('mom|yoy', names(df))) 

df1_long <- melt(df1, id.vars = 'date')
plot1 <- ggplot(df1_long[!is.na(df1_long$value), ],
       aes(x = date,
           y = value,
           col = variable)) +
  geom_line(size=0.6, alpha=0.5) +
  geom_point(size=1, alpha=0.8) +
  labs(
    x='',
    y='Unit: $'
  ) 

# MoM changes
df2 <- df %>%
  select(grep('date|mom', names(df)))

df2_long <- melt(df2, id.vars = 'date')
plot2 <- ggplot(df2_long[!is.na(df2_long$value), ],
       aes(x = date,
           y = value,
           col = variable)) +
  geom_line(size=0.6, alpha=0.5) +
  geom_point(size=1, alpha=0.8) +
  labs(
    x='',
    y='Unit: %'
  ) 

# YoY changes
df3 <- df %>%
  select(grep('date|yoy', names(df))) 

df3_long <- melt(df3, id.vars = 'date')
plot3 <- ggplot(df3_long[!is.na(df3_long$value), ],
       aes(x = date,
           y = value,
           col = variable)) +
  geom_line(size=0.6, alpha=0.5) +
  geom_point(size=1, alpha=0.8) +
  labs(
    x='',
    y='Unit: %'
  )
plot <- plot1 + plot2 + plot3 + plot_layout(ncol=1)
# plot <- plot_grid(plot1, plot2, plot3, labels = c('Value', 'MoM', 'YoY'), label_size = 12)
plot

Out:

My question is how could I convert code above to a function so I could easily apply it to new excel files with similar time series variables?

Thanks for your help at advance.