geom_bar plot with several variables

Question

[jordi.planells]

Hi all, I need your help. I am struggling on getting a bar plot with ggplot2 package.

Imagine I have 3 different variables (which would be my y values in aes) that I want to plot for each of my samples (x aes):

 str(df) 
'data.frame':   4 obs. of  4 variables:
 $ samples: Factor w/ 4 levels "S1","S2","S3",..: 1 2 3 4
 $ v1     : int  234 189 167 235
 $ v2     : int  345 265 235 254
 $ v3     : int  54 48 32 645

I would like to have a barplot in which I have a group per sample (4), each of them with 3 bars, one for each variable (12 bars in total). I know that if I want to extract the height from the df I have to call for stat = "identity". So far this has been my guess, but it's not working properly:

n <- ggplot(df) + 
  geom_bar(mapping = aes(x = samples, y = v1), stat = "identity", position = "dodge") + 
  geom_bar(mapping = aes(x = samples, y = v2), stat = "identity", position = "dodge") +
  geom_bar(mapping = aes(x = samples, y = v3), stat = "identity", position = "dodge")

Could you please help me?

Thanks before hand

[gpushpaganesan]

4 observation of 4 variables: I have Type position in more variable (20),how to give minimum variable(5)

[Kevin Blighe]

Excuse me...?

Answer 1

[cpad0112]

with iris data : 4 observation of 4 variables:

data(iris)
library(ggplot2)
library(tidyr)

iris %>%
  gather("Type", "Value",-Species) %>%
  ggplot(aes(Species, Value, fill = Type)) +
  geom_bar(position = "dodge", stat = "identity") +
  theme_bw()

Separate boxes for each species:

iris %>%
  gather("Type", "Value",-Species) %>%
  ggplot(aes(Species, Value, fill = Type)) +
  geom_col(position = "dodge") +
  theme_bw()+
  facet_wrap(~Species,scales = "free_x")

input (for one species, likewise for rest two species):

> head(iris)
  Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1          5.1         3.5          1.4         0.2  setosa
2          4.9         3.0          1.4         0.2  setosa
3          4.7         3.2          1.3         0.2  setosa
4          4.6         3.1          1.5         0.2  setosa
5          5.0         3.6          1.4         0.2  setosa
6          5.4         3.9          1.7         0.4  setosa

[Sam]

Hi, Wonderful explanations. Thanks! But like to know how to rearrange the variables in the each box. for example, petal.length, sepal.length, petal.width, sepal.width

Also how about display in descending order. Thanks

[Kevin Blighe]

You can re-order these by converting them to [ordered] factors in the input data.

[cpad0112]

look at the bottom figures of https://digibio.blogspot.com/2020/07/control-grouped-barcharts-in-ggplot.html