Why is geom_bar y-axis unproportional to actual numbers? - r

Question

Sorry if this question already exists - was googling for a while now already and didn't find anything.
I am relatively new to R and learning while doing all of this.
I'm supposed to create some PDF via r markdown that analyses patient-data with specific main-diagnosis and secondary-diagnosis. For this I'm supposed to plot some numbers via ggplot (geom_bar and geom_boxplot).
So what I do so far is, I retrieve data-sets that include both codes via SQL and load them into data.table-objects afterwards. Afterwards I join them to get the data I need.
After this I add columns that consist sub-strings of those codes and others that consist the count of those certain sub-strings (so I can plot the occurrences of every code).
I wanted now for example to put certain data.table into a geom_bar or geom_boxplot and make it visible. This actually works, but my y-axis has a weird scale that doesn't fit the numbers it actually should show. The proportions of the bars are also not accurate.
For example: one diagnoses appears 600 times and the other one 1000 times. The y-axis shows steps of 0 - 500.000 - 1.000.000 - 1.500.000 - ....
The Bar that shows 600 is super small and the bar with 1000 goes up to 1.500.000
If I create a new variable before and count what I need via count() and plot this it just works. The rows I put for the y-axis have in both variable the same datatype (integer)
So here is just how I create the data.table that I use for plotting
exazerbationsHdComorbiditiesNd <- allExazerbationsHd[allComorbiditiesNd, on="encounter_num", nomatch=0]
exazerbationsHdComorbiditiesNd <- exazerbationsHdComorbiditiesNd[, c("i.DurationGroup", "i.DurationInDays", "i.start_date", "i.end_date", "i.duration", "i.patient_num"):=NULL]
exazerbationsHdComorbiditiesNd[ , IcdHdCodeCount := .N, by = concept_cd]
exazerbationsHdComorbiditiesNd[ , IcdHdCodeClassCount := .N, by = IcdHdClass]
If I want to bar-plot now for example IcdHdClass by IcdHdCodeClassCount I do following:
ggplot(exazerbationsHdComorbiditiesNd, aes(exazerbationsHdComorbiditiesNd$IcdHdClass, exazerbationsHdComorbiditiesNd$IcdHdCodeClassCount, label=exazerbationsHdComorbiditiesNd$IcdHdCodeClassCount)) + geom_bar(stat = "identity") + geom_text(vjust = 0, size = 5)
It outputs said bar-plot with weird proportions.
If I do first:
plotTest <- count(exazerbationsHdComorbiditiesNd, exazerbationsHdComorbiditiesNd$IcdHdClass)
And then bar-plot it:
ggplot(plotTest, aes(plotTest$`exazerbationsHdComorbiditiesNd$IcdHdClass`, plotTest$n, label=plotTest$n)) + geom_bar(stat = "identity") + geom_text(vjust = 0, size = 5)
Its all perfect and works.
I checked also data-types of the columns I needed:
sapply(exazerbationsHdComorbiditiesNd, class)
sapply(plotTest, class)
In both variables the columns I need are of the type character and integer
Edit:
Unfortunately I cant post images. So here are just the links to those.
Here is a screenshot of the plot with wrong y-axis:
https://ibb.co/CbxX1n7
And here is a screenshot of the plot shown right:
https://ibb.co/Xb8gyx1
Here is some example-data that I copied out the data.table object:
Exampledata

Answer 1

Since you added the class counts as an additional column--rather than aggregating--what’s happening is that for each row in your data, the class counts get stacked on top of each other:
library(tidyverse)
set.seed(42)
df <- tibble(class = sample(letters[1:3], 10, replace = TRUE)) %>%
add_count(class, name = "count")
df # this is essentially what your data looks like
#> # A tibble: 10 x 2
#> class count
#> <chr> <int>
#> 1 a 5
#> 2 a 5
#> 3 a 5
#> 4 a 5
#> 5 b 3
#> 6 b 3
#> 7 b 3
#> 8 a 5
#> 9 c 2
#> 10 c 2
ggplot(df, aes(class, count)) + geom_bar(stat = "identity")
You could use position = "identity" so that the bars don’t get stacked:
ggplot(df, aes(class, count)) +
geom_bar(stat = "identity", position = "identity")
However, that creates a whole bunch of unnecessary layers in your plot that you can’t see. A better approach would be to drop the extra rows from your data before plotting:
df %>%
distinct(class, count)
#> # A tibble: 3 x 2
#> class count
#> <chr> <int>
#> 1 a 5
#> 2 b 3
#> 3 c 2
df %>%
distinct(class, count) %>%
ggplot(aes(class, count)) +
geom_bar(stat = "identity")
Created on 2019-09-05 by the reprex package (v0.3.0.9000)