How to delete legend in ggplot with reression model? - r

Question

I'd like to ask how to delete legend in ggplot with regression model.
I already added theme(legend.position = "None")
but the legend cannot be deleted. Could you tell me what I was doing wrong?
Extra question!!
In my current code, how to change the symbol size and shape between N0 and N1? I want more bigger size of 'open circle', and 'closed square' shape.
Many thanks!!!
ggplot(data=x, aes(x=agw, y=pgw)) +
geom_point (data=x, aes(x=agw, y=pgw, color=Nitrogen)) +
stat_smooth(method = 'lm', se=FALSE, color="Black") +
scale_color_manual(values = c("Dark gray","Black")) +
theme(legend.position = "None") +
geom_text(x=30, y=70, label="", size=3.5, col="Black") +
geom_text(x=30, y=60, label="", size=3.5, col="Black") +
scale_x_continuous(breaks = seq(0,80,10),limits = c(0,80)) +
scale_y_continuous(breaks = seq(0,80,10), limits = c(0,80)) +
theme_bw() +
theme(panel.grid = element_blank())

Answer 1

This should work in lack of reproducible data. Be careful that functions like theme_bw() use to remove previous theme() settings as mentioned by #Ronald. So it is better to add in the final part of the plot. For shapes, you can enable shape in aes() like this and format with scale_shape_manual() (the numbers inside belong to the shape you want):
library(ggplot2)
#Code
ggplot(data=x, aes(x=agw, y=pgw)) +
geom_point (data=x, aes(x=agw, y=pgw, color=Nitrogen,shape=Nitrogen,size=3)) +
stat_smooth(method = 'lm', se=FALSE, color="Black") +
scale_color_manual(values = c("Dark gray","Black")) +
scale_shape_manual(values = c(1,15))+
geom_text(x=30, y=70, label="", size=3.5, col="Black") +
geom_text(x=30, y=60, label="", size=3.5, col="Black") +
scale_x_continuous(breaks = seq(0,80,10),limits = c(0,80)) +
scale_y_continuous(breaks = seq(0,80,10), limits = c(0,80)) +
theme_bw() +
theme(panel.grid = element_blank(),
legend.position = 'none')

Answer 2

For the legend: add the argument show.legend = F inside geom_point. For the different point size: can you give us an example of your dataset? We may need to reshape it.
ggplot(data=x, aes(x=agw, y=pgw)) +
geom_point (data=x, aes(x=agw, y=pgw, color=Nitrogen), show.legend = F) +
stat_smooth(method = 'lm', se=FALSE, color="Black") +
scale_color_manual(values = c("Dark gray","Black")) +
theme(legend.position = "None") +
geom_text(x=30, y=70, label="", size=3.5, col="Black") +
geom_text(x=30, y=60, label="", size=3.5, col="Black") +
scale_x_continuous(breaks = seq(0,80,10),limits = c(0,80)) +
scale_y_continuous(breaks = seq(0,80,10), limits = c(0,80)) +
theme_bw() +
theme(panel.grid = element_blank())