# colors

### Too Many Colors Spoil the Graph

March 26th, 2024 by

When you draw a graph- either a bar chart, a scatter plot, or even a pie chart, you have the choice of a broad range of colors that you can use. R, for example, has 657 different colors from aliceblue to yellowgreen. SAS has 13 shades of orange, 33 shades of blue, and 47 shades of green. They even have different shades of black.

You have a wealth of colors, but you can’t use all of them in the same graph. The ideal number of colors is 2.

### R Graphics: Plotting in Color with qplot Part 2

January 13th, 2015 by

In the last lesson, we saw how to use qplot to map symbol colour to a categorical variable. Now we see how to control symbol colours and create legend titles.

```M <- structure(list(PATIENT = c("Mary","Dave","Simon","Steve","Sue","Frida","Magnus","Beth","Peter","Guy","Irina","Liz"), GENDER = c("F","M","M","M","F","F","M","F","M","M","F","F"), TREATMENT = c("A","B","C","A","A","B","A","C","A","C","B","C"), AGE =c("Y","M","M","E","M","M","E","E","M","E","M","M"), WEIGHT_1 = c(79.2,58.8,72.0,59.7,79.6,83.1,68.7,67.6,79.1,39.9,64.7,65.6), WEIGHT_2 = c(76.6,59.3,70.1,57.3,79.8,82.3,66.8,67.4,76.8,41.4,65.3,63.2), HEIGHT = c(169,161,175,149,179,177,175,170,177,138,170,165), SMOKE = c("Y","Y","N","N","N","N","N","N","N","N","N","Y"), EXERCISE = c(TRUE,FALSE,FALSE,FALSE,TRUE,FALSE,FALSE,TRUE,TRUE,FALSE,FALSE,TRUE), RECOVER = c(1,0,1,1,1,0,1,1,1,1,0,1)), .Names = c("PATIENT","GENDER","TREATMENT","AGE","WEIGHT_1","WEIGHT_2","HEIGHT","SMOKE","EXERCISE","RECOVER"), class = "data.frame", row.names = 1:12)```

M

```    PATIENT GENDER TREATMENT AGE WEIGHT_1 WEIGHT_2 HEIGHT SMOKE EXERCISE RECOVER
1     Mary      F         A   Y     79.2     76.6    169     Y     TRUE       1
2     Dave      M         B   M     58.8     59.3    161     Y    FALSE       0
3    Simon      M         C   M     72.0     70.1    175     N    FALSE       1
4    Steve      M         A   E     59.7     57.3    149     N    FALSE       1
5      Sue      F         A   M     79.6     79.8    179     N     TRUE       1
6    Frida      F         B   M     83.1     82.3    177     N    FALSE       0
7   Magnus      M         A   E     68.7     66.8    175     N    FALSE       1
8     Beth      F         C   E     67.6     67.4    170     N     TRUE       1
9    Peter      M         A   M     79.1     76.8    177     N     TRUE       1
10     Guy      M         C   E     39.9     41.4    138     N    FALSE       1
11   Irina      F         B   M     64.7     65.3    170     N    FALSE       0
12     Liz      F         C   M     65.6     63.2    165     Y     TRUE       1
```

Now let’s map symbol size to `GENDER` and symbol colour to `EXERCISE`, but choosing our own colours. To control your symbol colours, use the layer: `scale_colour_manual(values = c())` and select your desired colours. We choose red and blue, and symbol sizes 3 and 7.

`qplot(HEIGHT, WEIGHT_1, data = M, geom = c("point"), xlab = "HEIGHT (cm)", ylab = "WEIGHT BEFORE TREATMENT (kg)" , size = factor(GENDER), color = factor(EXERCISE)) + scale_size_manual(values = c(3, 7)) + scale_colour_manual(values = c("red", "blue"))`

Here is our graph with red and blue points:

Now let’s see how to control the legend title (the title that sits directly above the legend). For this example, we control the legend title through the name argument within the two functions `scale_size_manual()` and `scale_colour_manual()`. Enter this syntax in which we choose appropriate legend titles:

```qplot(HEIGHT, WEIGHT_1, data = M, geom = c("point"), xlab = "HEIGHT (cm)", ylab = "WEIGHT BEFORE TREATMENT (kg)" , size = factor(GENDER), color = factor(EXERCISE)) + scale_size_manual(values = c(3, 7), name="Gender") + scale_colour_manual(values = c("red","blue"), name="Exercise") ```

We now have our preferred symbol colour and size, and legend titles of our choosing.

That wasn’t so hard! In our next blog post we will learn about plotting regression lines in R.

David Lillis Ph. D. has taught R to many researchers and statisticians. His company, Sigma Statistics and Research Limited, provides both on-line instruction and face-to-face workshops on R, and coding services in R. David holds a doctorate in applied statistics.

### R Graphics: Plotting in Color with qplot

January 12th, 2015 by

In this lesson, let’s see how to use qplot to map symbol colour to a categorical variable.

Copy in the following data set (a medical data set relating to patients in a randomised controlled trial):