How to generate a legend without a plot

Question

I wanted to generate this legend without the plot so I can position it separately (I circled it in red):

I tried the suggestions in this page but they did not work.

I'm hoping to get something like this:

But the only way that I'm thinking of to be able to position this legend is by making separate legend and then add it to them as suggested here.

My code is here:

zmapp024 <-ggplot(plot_frame, aes(Var2, Var1, fill = value)) + 
  geom_tile(color = "white", position = position_dodge(), show.legend = TRUE) +
  geom_point(data = data.frame(Var2 = 1:4, Var1 = 0, value = 0), size = 4,
           aes(color = factor(Var2))) +
  geom_point(data = data.frame(Var2 = 1:4, Var1 = 0, value = 1), alpha = 0) +
  scale_color_manual(values = c("black", "forestgreen", "#DE2D29", "#3C57A8"),
                     labels = c(expression(
                         CD44^{lo}~"T Cells",
                         CD44^{hi}~CD69^{lo}~"T Cells",
                         CD44^{hi}~CD69^{hi}~CD103^{lo}~"T Cells",
                         CD44^{hi}~CD69^{hi}~CD103^{hi}~"T Cells")),
                     guide = guide_legend(override.aes = list(fill = NA), label.hjust = 0, position="bottom", size = 5 )) +

  scale_y_discrete(position = "right") +
  labs(y = "", fill = "", color = " ", x = "")  +
  scale_fill_gradientn(colors = c("#3C57A8", "white", "#DE2D29"),
                       breaks = c(1.5, 0, -1.5),
                       labels = c("1.0", "0", "-1.0"),
                       limits = c(-1.5, 1.5),
                       space = "Lab",
                       guide = "colourbar",
                       aesthetics = "fill") +
  theme_minimal() + 
theme (panel.grid.major = element_blank(), 
       axis.text.y.right = element_text(margin = margin(l = unit(-5, "cm"))),
       axis.text.y = element_text(face="italic", size=9, 
                                 color="black"),
       legend.justification = c(-0.9, 0),
       legend.direction = "vertical",
       legend.key.size = unit(0.6, "cm"),
       legend.key.width = unit(0.2,"cm"),
       legend.title.align = 0.5,
       axis.text.x = element_blank()) +
guides(
        fill = guide_colourbar(
            title = "Relative gene expression \n (z score)",
            title.position = "right",
            title.theme = element_text(angle = -90, size = 7.5),
            direction = "vertical",
            ticks = FALSE))

The dput of the data:

structure(list(Var1 = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 
8L, 9L, 10L, 11L, 12L, 13L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 
21L, 22L, 23L, 24L, 25L, 26L, 27L, 28L, 29L, 30L, 31L, 32L, 33L, 
34L, 35L, 36L, 37L, 38L, 39L, 40L, 41L, 42L, 43L, 44L, 45L, 46L, 
47L, 48L, 49L, 50L, 51L, 52L, 53L, 54L, 55L, 56L, 57L, 1L, 2L, 
3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L, 15L, 16L, 
17L, 18L, 19L, 20L, 21L, 22L, 23L, 24L, 25L, 26L, 27L, 28L, 29L, 
30L, 31L, 32L, 33L, 34L, 35L, 36L, 37L, 38L, 39L, 40L, 41L, 42L, 
43L, 44L, 45L, 46L, 47L, 48L, 49L, 50L, 51L, 52L, 53L, 54L, 55L, 
56L, 57L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 
13L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 21L, 22L, 23L, 24L, 25L, 
26L, 27L, 28L, 29L, 30L, 31L, 32L, 33L, 34L, 35L, 36L, 37L, 38L, 
39L, 40L, 41L, 42L, 43L, 44L, 45L, 46L, 47L, 48L, 49L, 50L, 51L, 
52L, 53L, 54L, 55L, 56L, 57L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 
9L, 10L, 11L, 12L, 13L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 21L, 
22L, 23L, 24L, 25L, 26L, 27L, 28L, 29L, 30L, 31L, 32L, 33L, 34L, 
35L, 36L, 37L, 38L, 39L, 40L, 41L, 42L, 43L, 44L, 45L, 46L, 47L, 
48L, 49L, 50L, 51L, 52L, 53L, 54L, 55L, 56L, 57L), .Label = c("Sdc4", 
"Ramp1", "Ptpn5", "Prdm1", "Pmaip1", "Myo1e", "Lamc1", "Itgb8", 
"Itgav", "Foxp3", "Dst", "Csf1", "Bmpr2", "Xcl1", "Vdr", "Tnfsf11", 
"Spry1", "Rbpj", "Ptprs", "Nrp1", "Il5", "Il4", "Il13", "Igfbp7", 
"Ifng", "Furin", "Ern1", "Vim", "Tiam1", "Podnl1", "Penk", "Maf", 
"Lmna", "Il2ra", "Il1rl1", "Il10", "Id2", "Ehd1", "Csda", "Cd44", 
"Ccr2", "Capg", "Calca", "Bcl2l1", "Areg", "Adam8", "S100a6", 
"S100a4", "Rora", "Mki67", "Lgals1", "Il2rb", "Hist1h1b", "Anxa2", 
"Itgb1", "Esm1", "S100a10"), class = "factor"), Var2 = c(1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L), value = c(-0.716873478395867, -0.919984230086674, 
-0.661176149944064, -0.828193431806995, -0.990890861695874, -0.985855800232094, 
-0.823026349552051, -0.608384425062877, -0.809200195330501, -0.621395373041386, 
-0.998621039674651, -0.795949946272161, -1.10479976781604, -0.499510689498092, 
-0.680578082389661, -0.850155027403529, -1.02359795075789, -0.930715054575906, 
-0.900246349411412, -1.12696248565925, -0.531673076619624, -0.634387083227473, 
-0.567814470617106, -0.704971739502355, -0.77107142771167, -1.0577165116177, 
-1.12689193292486, -1.07046845292562, -1.21970205863578, -1.06946734340346, 
-0.697966304450698, -1.31865479289137, -1.1644549788312, -0.724572318411187, 
-0.887650620239559, -0.878042971979847, -0.898835722780145, -0.966547257168572, 
-1.44089646981222, -1.17641689690512, -0.981496097411318, -0.949054521097622, 
-0.86984148513583, -1.03997550896008, -0.776245072529661, -0.926869652178528, 
-1.22014851883998, -1.11565223232092, -1.45758806540816, -1.30893449397075, 
-1.38003602497654, -1.224949334573, -1.38357974363453, -1.35339938422864, 
-0.968416032914201, -0.65165652813915, -1.4919639415255, -0.685400251755411, 
-0.802640661038347, -0.575837610054767, -0.629465888711167, -0.317915043043598, 
-0.559729515180935, -0.422625579063628, -0.503276458166707, -0.565387197269664, 
-0.414441446968764, -0.652570443296679, -0.699718481126342, -0.587483551485666, 
-0.479784066762678, -0.474739880805875, -0.163485068386743, -0.0319151401130408, 
-0.687844415173434, -0.793272191522238, -0.192431267926848, -0.478440062610096, 
-0.406493550612629, -0.516470014019787, -0.516293205774877, -0.0703527612407989, 
-0.321528054118583, -0.417459180983822, -0.410868262057476, -0.333210832661548, 
-0.61740991961346, -0.605534106803515, -0.228283398359129, -0.490846073129063, 
-0.588893105208149, -0.691611619542831, -0.768211373139653, -0.655714376336414, 
-0.691777405043065, 0.27283725214197, -0.46762324186072, -0.663659775386651, 
-0.595353641454884, -0.813248687573964, -0.672352278644248, -0.649282500217443, 
-0.722482130363645, -0.325408266036161, -0.49770614745867, 0.177675109919899, 
0.206312208622598, -0.0834329896761757, -0.400018473948618, 0.627959745919098, 
0.639468920429142, 0.881985828293655, 1.4894632640724, 0.564376769280816, 
-0.0175886218831413, 0.748001124892129, -0.237693188616826, 0.0748099685432856, 
-0.0738067160244709, 0.262707416774023, -0.204274564295389, -0.381902355833725, 
-0.047820862385917, -0.458203252153174, 0.498723523113106, 0.13206419664028, 
0.811723606016846, 1.49979274596739, 1.48431659019814, 1.43869340350301, 
1.36267422579482, 1.2280707677281, 1.09802917518633, 1.30099479431717, 
1.49960551175132, 1.4927056563283, 1.49686976804331, 1.47397253453575, 
1.43227082074503, 1.3325444408283, 1.1983987520954, 0.198402134411653, 
1.08912853827601, 1.00509721706754, -0.153425140424883, 0.852612722881043, 
0.698995996122549, -0.138755915285969, 0.296318265086462, 0.446421081491043, 
0.251052659372192, 0.50342451499526, 0.873163189823561, 0.6704650702465, 
0.474043909647662, 0.24672752839951, 1.12930018666821, 0.869584307302813, 
0.0200115056815992, 0.46498720236421, 0.447990671026386, 0.485629347319394, 
0.528646313252754, -0.0127091863060346, 0.637743076608102, 0.910524864813588, 
-0.0726857435537057, 0.859230754317892, 0.843382686575065, -0.364665784858882, 
0.351291400617603, 1.41986247931586, 0.974623726851428, 1.47470660621924, 
1.38284919037663, 1.38261262076394, 1.28287812909918, 1.4499266152937, 
1.493563316646, 1.42240835251479, 1.49404009657185, 1.15246823659118, 
1.36360436969755, 0.880559849096722, -0.520497871814678, -0.328998889961762, 
-0.425053223809833, -0.307160868594853, 0.390488791334733, 0.595489070523626, 
0.0183991764982231, -0.489492083871666, -0.451824932137866, -0.412585283406412, 
-0.252707589258521, -0.5908467120367, 0.0467001829831055, 0.345952361813286, 
1.28293458057144, 0.463784556661154, 0.681779946448773, 1.45692561131772, 
0.69432543075946, 0.956305055837712, 1.45222131165832, 1.28294398902894, 
1.19983334411133, 1.30349742116338, 1.15489996934721, 0.294895869208661, 
0.973575068519344, 1.17111204440007, 1.297680661103, 0.553790085627175, 
0.842743233449211, 1.40551605194952, 1.184364466613, 1.09756610180677, 
1.12772904683868, 0.751266682827816, 1.11533140667713, 0.825725901866236, 
0.714442943708028, 0.828305803894246, -0.145300290518389, -0.756952453676937, 
-0.473140866248911, 0.576295750132076)), class = "data.frame", row.names = c(NA, 
-228L))

This is what I tried:

legend <- cowplot::get_legend(zmapp024)

grid.newpage()
grid.draw(legend)

Hi there. This looks similar to a previous question of yours that I answered. What was the problem? — Allan Cameron, Nov 19 '20 at 18:37
Have you tried just running the `legend` function without plotting anything? — , Nov 19 '20 at 21:04
Thank you @AllanCameron there were two problem, I can't remove the the lines extending from the plot next to the dots, the second is the size of the dots in the legend, I want to make them small, and keep the size of the dots underneath the plot large. — user432797, Nov 19 '20 at 21:45

score 3 · Accepted Answer · answered Nov 19 '20 at 22:16

It's clear you're not giving up until you get this plot exactly the way you want it, so let's iron out some of the creases:

You can remove the gridlines with theme(panel.grid = element_blank())
You can remove the faint gray behind the points in the legend if you do theme(legend.key = element_blank())
You can get rid of the legend title with theme(legend.title = element_blank())
You can set the size of the points in the legend by putting size = inside the override.aes argument of guide_legend
You can add the extracted legend using annotation_custom.

Putting all this together (and without simplifying the rest of your code) we have:

zmapp023 <- ggplot(plot_frame, aes(Var2, Var1, fill = value)) + 
  geom_tile(color = "white", position = position_dodge(), show.legend = TRUE) +
  geom_point(data = data.frame(Var2 = 1:4, Var1 = -1, value = 0), size = 5,
           aes(color = factor(Var2))) +
  geom_point(data = data.frame(Var2 = 1:4, Var1 = 0, value = 1), alpha = 0) +
  scale_color_manual(values = c("black", "forestgreen", "#DE2D29", "#3C57A8"),
                     labels = c(expression(
                         CD44^{lo}~"T Cells",
                         CD44^{hi}~CD69^{lo}~"T Cells",
                         CD44^{hi}~CD69^{hi}~CD103^{lo}~"T Cells",
                         CD44^{hi}~CD69^{hi}~CD103^{hi}~"T Cells")),
                     guide = guide_legend(override.aes = list(fill = NA), 
                                          label.hjust = 0, position="bottom", size = 5)) +

  scale_y_discrete(position = "right") +
  labs(y = "", fill = "", color = " ", x = "")  +
  scale_fill_gradientn(colors = c("#3C57A8", "white", "#DE2D29"),
                       breaks = c(1.5, 0, -1.5),
                       labels = c("1.0", "0", "-1.0"),
                       limits = c(-1.5, 1.5),
                       space = "Lab",
                       guide = "colourbar",
                       aesthetics = "fill") +
  theme_minimal() + guides(colour=FALSE) +
theme (panel.grid = element_blank(), 
       axis.text.y.right = element_text(margin = margin(l = unit(-5, "cm"))),
       axis.text.y = element_text(face="italic", size=9, 
                                 color="black"),
       legend.justification = c(-0.9, 0),
       legend.direction = "vertical",
       legend.key.size = unit(0.6, "cm"),
       legend.key.width = unit(0.2,"cm"),
       legend.title.align = 0.5,
       axis.text.x = element_blank(),plot.margin = unit(c(1,1,5,1), "lines")) +
guides(
        fill = guide_colourbar(
            title = "Relative gene expression \n (z score)",
            title.position = "right",
            title.theme = element_text(angle = -90, size = 7.5),
            direction = "vertical",
            ticks = FALSE)) +
coord_cartesian( # This focuses the x-axis on the range of interest
                      clip = 'off')

legend1 <- ggplot(plot_frame, aes(Var2, Var1)) +
  geom_point(data = data.frame(Var2 = 1:4, Var1 = 0, value = 0), size = 5,
           aes(color = factor(Var2))) +
  geom_point(data = data.frame(Var2 = 1:4, Var1 = 0, value = 1), alpha = 0) +
  scale_color_manual(values = c("black", "forestgreen", "#DE2D29", "#3C57A8"),
                     labels = c(expression(
                         CD44^{lo}~"T Cells",
                         CD44^{hi}~CD69^{lo}~"T Cells",
                         CD44^{hi}~CD69^{hi}~CD103^{lo}~"T Cells",
                         CD44^{hi}~CD69^{hi}~CD103^{hi}~"T Cells")),
                     guide = guide_legend(override.aes = list(size = 3), 
                                          label.hjust = 0)) + 
theme (panel.grid = element_blank(), 
       axis.text.y.right = element_text(margin = margin(l = unit(-5, "cm"))),
       axis.text.y = element_text(face="italic", size=9, 
                                 color="black"),
       legend.justification = c(-0.5, 0),
       legend.direction = "vertical",
       legend.key = element_blank(),
       legend.title = element_blank(),
       axis.text.x = element_blank())

legend <- cowplot::get_legend(legend1)
zmapp023 + annotation_custom(legend$grobs[[1]], xmin = 5, ymax = -9)

I don't know how to thank you @AllanCameron ... I appreciate your support! — user432797, Nov 20 '20 at 07:03

How to generate a legend without a plot

1 Answers1