I'm plotting 2 variables (frequency and fold change) by geom\_point. As in the figure below, the size corresponds to the frequency and colour to the fold change (FC <1.5 = green, >1.5 = red). To distinguish fold change below 1, I have introduced more breaks. The plot turns out as expected, but I am wondering if there is a way to make the scale at the legend to be equally spaced for the breaks corresponding to this scale `c(0, 0.25, 0.5, 0.75, 1, 2, 3, 4, 5, 6)` (see "Desired scale" on the right of the plot). Does anyone knows how to achieve this? Thanks a lot in advanced!

[![enter image description here](https://i.stack.imgur.com/XIxYy.png)](https://i.stack.imgur.com/XIxYy.png)

Below is the code for the plot.

```
p <- ggplot(mainG, aes(x = Allele, y = Cohort, size = Freq, color = FC)) +
  geom_point() +
  scale_y_discrete(limits = rev(levels(mainG$Cohort)), position = "right") +
  scale_size_continuous(limits = c(0, 0.5), breaks = c(0, 0.05, 0.10, 0.20, 0.40)) +
  # Underrepresented: FC < 1.5 ; overrepresented: FC > 1.5
  scale_colour_gradientn(
    colours = c('darkgreen', 'forestgreen', 'darkseagreen3', 'darkseagreen2',
              'indianred1', 'indianred2', 'indianred3', 'darkred'),
    values = c(0, 0.25, 0.5, 0.75, 1, 2, 3, 4, 5, 6)/6,
    breaks = c(0, 0.25, 0.5, 0.75, 1, 2, 3, 4, 5, 6)) +
  xlab("") + ylab("") +
  theme(axis.text = element_text(size = 7),
        axis.text.x = element_text(angle = 45, vjust = 1, hjust=1),
        axis.ticks.y = element_blank(),
        panel.border = element_rect(fill = NA),
        panel.background = element_blank(),
        axis.line = element_line(), 
        legend.title = element_text(size = 7),
        legend.text = element_text(size = 7),
        legend.key = element_blank(), 
        legend.position = "right",
        panel.spacing = unit(0.2, "lines"), 
        strip.background =element_rect(colour = "black", fill = NA),
        strip.text = element_text(size = 7, face = "bold", margin = margin(0.1,5,0.1,5, "cm"))
  ) +
  facet_grid(.~ Gene, scales = "free", space = "free")

p + guides(colour = guide_colourbar(barwidth = unit(0.5, "cm"), barheight = unit(5, "cm"), 
                                    direction = "vertical"),
           size = guide_legend(title = "Frequency", reverse = T))

```

Edit: here's the sample data of mainG for reproducibility (sorry the section is becoming lengthy...)

```
Cohort  Gene    Allele  Freq    FC
Cohort1 B   *08:01  0.027   0.24
Cohort2 A   *01:01  0.103   0.63
Cohort2 A   *68:01  0.103   3.63
Cohort2 B   *07:02  0.207   1.59
Cohort2 B   *08:01  0.034   0.31
Cohort2 B   *51:01  0.121   2.44
Cohort3 A   *02:01  0.407   1.51
Cohort3 A   *03:01  0   NA
Cohort3 B   *07:02  0.037   0.28
Cohort3 B   *08:01  0.019   0.17
Cohort3 B   *44:03  0.148   3.15
Cohort4 A   *02:01  0.17    0.63
Cohort4 A   *24:02  0.17    2.01
Cohort4 B   *07:02  0.05    0.38
Cohort4 B   *18:01  0.11    2.41
Cohort5 B   *07:02  0.053   0.4
Cohort5 B   *18:01  0.105   2.31
Cohort6 B   *07:02  0.041   0.31
Cohort6 B   *18:01  0.122   2.69
Cohort6 B   *51:01  0.102   2.06
Control A   *01:01  0.163   NA
Control A   *02:01  0.269   NA
Control A   *03:01  0.14    NA
Control A   *24:02  0.085   NA
Control A   *26:01  0.035   NA
Control A   *29:02  0.035   NA
Control A   *32:01  0.037   NA
Control A   *68:01  0.029   NA
Control B   *07:02  0.13    NA
Control B   *08:01  0.11    NA
Control B   *18:01  0.046   NA
Control B   *44:02  0.087   NA
Control B   *44:03  0.047   NA
Control B   *51:01  0.05    NA

```