I use ggplot() + geom_line() function to draw a line plot for girls.
When I create the plot for girls it shows well as below.
But I cannot combine two line plots( both boys and girls) by " +". It shows the errors as below.
Does anyone know what I need to do for combining these two plots?
I use ggplot() + geom_line() function to draw a line plot for girls. When I create the plot for girls it shows well as below.![image](https://user-images.githubusercontent.com/63035655/90161661-0a0b5780-ddc6-11ea-97e5-b8e0226f315e.png)
But I cannot combine two line plots( both boys and girls) by " +". It shows the errors as below. Does anyone know what I need to do for combining these two plots?![image](https://user-images.githubusercontent.com/63035655/90162081-ae8d9980-ddc6-11ea-82ad-24dd31f8f06f.png)