Changing the shape of one point or few points in a scatter plot in R based off of character values

Question

I would like to have a scatter plot where different shape sizes show the different localities (only two localities).

The data is presented here:

Sample Name εNd stratigraphic column    sample number
B8  -4.887223024    8.34    ND
B7B8    -5.723139056    8.27    ND
MO2400  -6.639290394    7.2 M
SHARK 2 -6.349256446    7   M
M.FISH  -6.100998712    7.1 M
MO2376  -7.689046402    -6  M
ABOVE UPPER -8.306593254    -6.53   ND
NIO 38  -8.90688489 -8.07   ND
NIO 39  -7.243909917    -8.16   ND
T-4 TO T-5  -7.700379025    -12 ND
T-2 TO T-3  -8.532019275    -12.47  ND
T1 TO T0    -6.894687774    -13.1   ND

I have tried using this code:

ggplot(data=nd, aes(x=nd$εNd, y= nd$`stratigraphic column`)) + geom_point(size=4, shape=factor(nd$`sample number`))+ggtitle(expression(epsilon*"Neodymium in Manitoba Escarpment"))+xlab(~epsilon*"Nd")

And it gives me this graph:

I didn't like how the shapes looked, and had no legend. So I tried going a different route using the group in ggplot:

ggplot(data=nd, aes(x=εNd, y= `stratigraphic column`, group='sample number')) + geom_point(aes(shape='sample number'), size=4)+ scale_shape_manual(values=c(16,17))+ ggtitle(expression(epsilon*"Neodymium in Manitoba Escarpment")) + xlab(~epsilon*"Nd")+ylab("Stratigraphic Position")

And I got this as an output graph:

This one does not change the shapes based off of location, but has a legend.

I have tried changing my data type for the 'sample number' column from character to factor, and that didn't help.

Thanks in advance.

Answer 1

You need to map your sample number to the shape aesthetic:

ggplot(nd, aes(εNd, `stratigraphic column`)) + 
  geom_point(size = 4, aes(shape = `sample number`)) +
  ggtitle(expression(epsilon*"Neodymium in Manitoba Escarpment")) +
  xlab(~epsilon*"Nd") +
  theme_light()

---

Data in reproducible form as taken from question

nd <- structure(list(`Sample Name` = c("B8", "B7B8", "MO2400", "SHARK 2", 
"M.FISH", "MO2376", "ABOVE UPPER", "NIO 38", "NIO 39", "T-4 TO T-5", 
"T-2 TO T-3", "T1 TO T0"), eNd = c(-4.887223024, -5.723139056, 
-6.639290394, -6.349256446, -6.100998712, -7.689046402, -8.306593254, 
-8.90688489, -7.243909917, -7.700379025, -8.532019275, -6.894687774
), `stratigraphic column` = c(8.34, 8.27, 7.2, 7, 7.1, -6, -6.53, 
-8.07, -8.16, -12, -12.47, -13.1), `sample number` = c("ND", 
"ND", "M", "M", "M", "M", "ND", "ND", "ND", "ND", "ND", "ND")), 
class = "data.frame", row.names = c(NA, -12L))