Paul Z - 4 months ago 13

R Question

I am designing a bar plot with

`ggplot2`

The only problem is that I cannot get rid of the space between the bars and the x-axis.

I know that this formula should resolve the problem:

`scale_y_continuous(expand = c(0, 0)) function`

But it seems that the element for the error bar is overwriting it and gives always this space.

here my code:

`p<-ggplot(data=tableaumergectrlmut, aes(x=ID, y=meanNSAFbait, fill=Condition)) +`

geom_bar(stat="identity", position=position_dodge())+

scale_y_continuous(expand = c(0,0))+

geom_errorbar(aes(ymin=meanNSAFbait-SDNSAFbait,

ymax=meanNSAFbait+SDNSAFbait, width=0.25), position=position_dodge(.9))

Answer

Using some example data to generate a plot that (I think) shows the problem you're having.

```
library(ggplot2)
df <- data.frame(val = c(10, 20, 100, 5), name = LETTERS[1:4])
ggplot(df, aes(x = name, y = val, fill = name)) +
geom_bar(stat = "identity")
```

There is a gap from the zero point on the y axis (bottom of the bars) and where the x axis labels are.

You can remove this using `scale_y_discrete`

or `scale_y_continuous`

, depending on the nature of your data, and setting `expand`

to `c(0,0)`

:

```
ggplot(df, aes(x = name, y = val, fill = name)) +
geom_bar(stat = "identity") +
scale_y_discrete(expand = c(0,0)) +
scale_x_discrete(expand = c(0,0))
```

This gives the plot:

Note I've also removed the gap along the y axis, simply remove the `scale_x_discrete`

line to add this gap back in.

Since error bars are an issue, here are a few examples:

```
ggplot(df, aes(x = name, y = val, fill = name)) +
geom_bar(stat = "identity") +
geom_errorbar(aes(ymin = val - 10,
ymax = val + 10))
```

You can use scale to remove the padding down to the error bar:

```
ggplot(df, aes(x = name, y = val, fill = name)) +
geom_bar(stat = "identity") +
geom_errorbar(aes(ymin = val - 10,
ymax = val + 10)) +
scale_y_continuous(expand = c(0,0))
```

Or you can use coord_cartesian to give a hard cutoff:

```
ggplot(df, aes(x = name, y = val, fill = name)) +
geom_bar(stat = "identity") +
geom_errorbar(aes(ymin = val - 10,
ymax = val + 10)) +
scale_y_continuous(expand = c(0,0)) +
coord_cartesian(ylim = c(0, max(df$val) + 10))
```