Changing a wide range of colours to a limited gradient

Question

I returned a FeaturePlot from Seurat to ggplot. My plot has a weird range of colours as below

I produced this plot by this code

> head(mat[1:4,1:4])
             s1.1        s1.2 s1.3       s1.4
DDB_G0267178    0 0.009263254    0 0.01286397
DDB_G0267180    0 0.000000000    0 0.00000000
DDB_G0267182    0 0.000000000    0 0.03810585
DDB_G0267184    0 0.000000000    0 0.00000000
> 

I have converted expression matrix to a binary matrix by 2 as a threshold

mat[mat < 2] <- 0
mat[mat > 2] <- 1

> head(exp[1:4,1:4])
             s1.1 s1.2 s1.3 s1.4
DDB_G0267382    0    0    0    1
DDB_G0267438    0    0    0    1
DDB_G0267466    0    0    0    0
DDB_G0267476    0    0    1    0
> 
> exp=colSums(exp)
> exp=as.matrix(exp)
> colnames(exp)="value"
> exp=as.data.frame(exp)
> cc <- AddMetaData(object = seurat, metadata = exp)
> cc <- SetAllIdent(object = cc, id = "value")
> TSNEPlot(object = cc, do.return= TRUE)

How I can convert this range to a gradient of colours for example in 8-18, 18-28, 28-38, 38-48 range in blue to yellow please? Something like below

Thank you for any help

Then by ggplot now I scaled my colours but I don't like my clusters as so and I don't know how to retain my clusters as a featureplot by this new color gradient

> head([email protected])
     nGene    nUMI    orig.ident res.0.7 CELL STAGE GENO dataset stage.nice celltype value
s1.1  4331  373762 SeuratProject       0 s1.1   H16   WT       1        H16        0    34
s1.2  5603 1074639 SeuratProject       0 s1.2   H16   WT       1        H16        0    26
s1.3  2064   49544 SeuratProject       0 s1.3   H16   WT       1        H16        0    27
s1.4  4680  772399 SeuratProject       1 s1.4   H16   WT       1        H16        1    29
s1.5  3876  272356 SeuratProject       1 s1.5   H16   WT       1        H16        1    21
s1.6  2557  122314 SeuratProject       0 s1.6   H16   WT       1        H16        0    31

> ggplot(as.data.frame([email protected]), aes(x = [email protected]$CELL, y = [email protected]$res.0.7, colour [email protected]$value)) + 
+     geom_point(size = 5) +
+     scale_colour_gradient(low = "yellow", high = "blue")

By below code I obtained a tsne in link

> cols <-  scales::seq_gradient_pal(low="beige", high="red", space="Lab")(seq(from=0, to=1,length.out=48))
> 
> TSNEPlot(cc, colors.use=cols)

enter link description here

Now I want to know how I could convert this range to a 8-18, 18-28, 28-38, 38-48 colour range as a gradient of blue to yellow?

Answer 1

If you would like to color discrete intervals on a gradient as opposed to having a continuous gradient (like your second plot), use this approach.

It is similar to the approach in the answer I posted with the continuous scale, but we simply break up the continuous scale in to intervals and color them by these intervals.

#generate values for testing purposes, one value for each cell, add to object
value <- sample(seq(from=8, to=46, by=1), size = length(rownames([email protected])), replace=TRUE)
exp <- AddMetaData(object=exp, metadata=value, col.name="value")

#encode the continuous values as factors, determined by the interval they fall in to
value_breaks <- cut([email protected]$value, breaks = c(8,18,28,38,46), include.lowest=TRUE, right=FALSE)

#name the breaks by cell so they can be added by AddMetaData(), add them
names(value_breaks) <- rownames([email protected])
exp <- AddMetaData(object=exp, metadata=value_breaks, col.name="value_breaks")

exp <-  SetIdent(exp, [email protected]$value_breaks)

#create a gradient between specified intervals
#length.out is the number of different colors, number of factor levels
cols <- scales::seq_gradient_pal(low="blue", high="yellow", space="Lab")(seq(from=0, to=1,length.out=4))

TSNEPlot(exp, colors.use=cols)

The label in the legend are classic mathematical notation for intervals. You can add your own labels if you wish in the cut() function.

Answer 2

TSNEPlot()

TSNEPlot() will always treat your variables as discrete. My approach is to manually generate a gradient with unique colors for each factor level and pass it to the cols.use argument in TSNEPlot().

#generate values for testing purposes, one value for each cell
value <- sample(seq(from=8, to=48, by=1), size = length(rownames([email protected])), replace=TRUE)
names(value) <- rownames([email protected])
exp <- AddMetaData(object=exp, metadata=value, col.name="value")
exp <-  SetIdent(exp, [email protected]$value)
#create a gradient between specified colors, multiply by sequence to get appropriate length
#length.out is the number of different colors, number of factor levels
cols <-  scales::seq_gradient_pal(low="beige", high="red", space="Lab")(seq(from=0, to=1,length.out=48))


TSNEPlot(exp, colors.use=cols)

I would present this with no legend:

TSNEPlot(exp, colors.use=cols, no.legend = TRUE)

FeaturePlot()

You can also simply use FeaturePlot() instead of TSNEPlot() to visualize the gradient. Using the same data as above:

FeaturePlot(object = exp, features.plot = "value", reduction.use = "tsne", no.legend = FALSE, cols.use = c("beige", "red"))

You ask for a continuous scale, but this is not what is shown in your second plot. You have a different color for each discrete range of values. I assume here that you want a continuous gradient. To achieve something like the second plot you provided requires a different approach.