R ggplot2 Bar Chart on Multiple Columns

Question

This seems so simple, but there is something fundamental I am not getting here. I have a dataframe with counts of some event per month as columns, per year as rows. Like this:

season  sep oct nov dec jan feb
2000    2   7   47  152 259 140
2001    1   5   88  236 251 145
2002    2   14  72  263 331 147
2003    5   6   71  207 290 242

First, I would like to create a bar chart for one season. For example, for the 2000 season, a bar chart showing the values for each month as a vertical bar (alas, not enough rep points to post an image of an example). I'm guessing I need to reshape my data in some way?

Ultimately I would like to create a facet wrapped set of charts, one for each season.

Please note I found a similar post, but the post was over complicated due to a lack of clarity on the question.

@user20650 - yes, thank you. See my comment below. My lack of fundamentals and understanding melt is my problem here. — aspergerboy
– aspergerboy, Commented Apr 11, 2015 at 14:21

DatamineR · Accepted Answer · 2015-04-11 14:45:30Z

5

library(reshape2)
library(ggplot2)
df_m <- melt(df, id.vars = "season")

In order to plot for one season (e.g. 2000)

ggplot(subset(df_m, season == "2001"), aes(x = variable, y = value)) +
geom_bar(stat = "identity")

And for facet wrapped set of charts try:

ggplot(df_m, aes(x = variable, y = value)) + geom_bar(stat = "identity") +
facet_wrap(~season)

enter image description here

edited Apr 11, 2015 at 14:45

answered Apr 11, 2015 at 13:37

DatamineR

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2 Comments

aspergerboy Over a year ago

Thank you very much @RStudent. From my perspective you should change your name to RMaster! FYI, I am quite new at this and felt I needed to pay more attention to first understanding vectors, lists, arrays and data frames, but graphs are so much fun. Ultimately I jumped ahead, but your demonstration of melt helped me understand I need to go back to fundamentals. I want to really understand the how/why here.

Lilly Over a year ago

Thank you a lot @DatamineR! Very useful "melt" function

Tyler Rinker · Accepted Answer · 2015-04-11 14:06:46Z

2

Here's a tidyr/dplyr approach:

if (!require("pacman")) install.packages("pacman")
pacman::p_load(dplyr, tidyr, ggplot2)

dat %>%
    gather(month, value, -season) %>%
    ggplot(aes(y = value, x = month)) +
    geom_bar(stat = "identity") +
    facet_wrap(~season)

enter image description here

edited Apr 11, 2015 at 14:06

answered Apr 11, 2015 at 13:42

Tyler Rinker

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1 Comment

aspergerboy Over a year ago

I like that. Thanks. I have been reading about dplyr and it seems much more accessible to me. For kicks I would like to plot all fours years, in order by month on one chart, but I won't ask - I will try and figure this out. I find learning R is best when it is with data that I am actually familiar with.

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