ggplot2：无法更改图例的标题

Question

I am unable to change the legend title in this graph with this data.

df <- structure(list(year = structure(c(1L, 1L, 2L, 2L, 2L, 3L, 3L, 
3L), .Label = c("2015", "2016", "2017"), class = "factor"), Category2 = c("grower", 
"starter", "grower", "layer", "starter", "grower", "layer", "starter"
), per_pound = c(0.2072, 0.382, 0.172, 0.173, 0.3705, 0.178667, 
0.1736, 0.277375)), .Names = c("year", "Category2", "per_pound"
), row.names = c(NA, -8L), vars = "year", drop = TRUE, class = c("grouped_df", 
"tbl_df", "tbl", "data.frame"))

And the graph I'm creating...

library (ggplot2)
p <- ggplot (data=df, aes(x=year, y=per_pound, group=Category2, color=Category2)) + geom_line() + geom_point()
p <- p + scale_fill_discrete(name="TEST")
p

Which is yielding this...

The legend name should be 'TEST' not 'Category2'. There must be something wrong with the data in the data frame but I haven't found the culprit.

-cherrytree

Answer 1

fill is for the interior colouring, while color is for outline. Some geom , such as geom_bar , can take both color and fill . We can change the outline of the bar using color , and the interior color using fill . However, some geom only take color , such as geom_line and geom_point , because there are no interior color to "change".

In your code, you specified the color using color=Category2 . That is correct. However, you will then use scale_color_discrete(name="TEST") accordingly. The following code will work.

library (ggplot2)
p <- ggplot (data=df, aes(x=year, y=per_pound, group=Category2, color=Category2)) + geom_line() + geom_point()
p <- p + scale_color_discrete(name="TEST")
p  

Answer 2

您还可以使用手动更改图例标题

p + guides(color=guide_legend(title="Whatever You Want"))