Adding custom regression line with set intercept and slope to ggplot

Question

I have created a plot using the following code:

ggplot(Data, aes(x=damMean, y=progenyMean)) + 
    geom_point()

I want to overlay on the plot a regression line of the form: y = 69.88 + 5.58*x

I tried to do so by adding the following:

ggplot(Data, aes(x=damMean, y=progenyMean)) + 
    geom_point() + 
    geom_smooth(method = "lm", formula = y~69.88+5.58*x)

But this doesn't add a line to the plot.

Is this possible to do using ggplot?

@DaveArmstrong this doesn't seem to have worked. There isn't any error message but the abline doesn't show on the graph — codemachino
– codemachino, Commented Aug 25, 2021 at 17:03
Just posted an answer that works for me. I think the problem is that the regression line is not actually in the window. For example, 5.58*40 + 69.88=289.88. So, the line will contain the point (40,289.88). Your y-axis only goes to around 110, so the line is not contained within the plotting region. — DaveArmstrong
– DaveArmstrong, Commented Aug 25, 2021 at 17:10

DaveArmstrong · Accepted Answer · 2021-08-25 17:07:41Z

3

Here's an example with some fake data:

mydat <- tibble(x=runif(100, 40, 90), 
                y = 80 + 5.5*x + rnorm(100, 0, 10))

ggplot(mydat, aes(x=x, y=y)) + 
  geom_point() + 
  geom_abline(slope=5.58, intercept=69.88)

answered Aug 25, 2021 at 17:07

DaveArmstrong

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2 Comments

codemachino Over a year ago

That looks great. Is there a reason why my geom_abline(slope=5.58, intercept=69.88) isn't showing on the plot?

DaveArmstrong Over a year ago

See comment above.

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