Kacey - 4 months ago 28

R Question

I can't seem to figure out the command for changing the x- and y-axes to go from 200-800 in increments of 100. (new to R, don't know how to provide large amounts of data)

`SAT <- read.csv(file.choose(), header = TRUE)`

SAT2 <- na.exclude(SAT)

SAT.MV <- SAT2[,1:2]

plot(SAT.MV$VSAT,SAT.MV$MSAT,main="Math and Verbal SAT Scores",xlab="Verbal Score",

ylab="Math Score")

head(SAT.MV)

SAT.MV.3means <- kmeans(SAT.MV,centers=3)

SAT.MV.3means$centers

SAT.MV.3means$cluster

plot(SAT.MV[SAT.MV.3means$cluster == 1, ], col = "red",

xlim=c(min(SAT.MV[ ,1]),max(SAT.MV[ ,1])),

ylim=c(min(SAT.MV[ ,2]),max(SAT.MV[ ,2])))

points(SAT.MV[SAT.MV.3means$cluster == 2,], col = "blue")

points(SAT.MV[SAT.MV.3means$cluster == 3,], col = "seagreen")

points(SAT.MV.3means$centers,pch=2, col = "black")

plot(SAT.MV[SAT.MV.3means$cluster == 1, ], col = "red",

xlim=c(min(SAT.MV[ ,1]),max(SAT.MV[ ,1])),

ylim=c(min(SAT.MV[ ,2]),max(SAT.MV[ ,2])))

points(SAT.MV[SAT.MV.3means$cluster == 2,], col = "blue")

points(SAT.MV[SAT.MV.3means$cluster == 3,], col = "seagreen")

points(SAT.MV.3means$centers,pch=2, col = "black")

Answer

Suppose I have a small data set:

```
dd <- data.frame(x=c(300,700,1000),y=c(-100,200,700))
```

I want to plot this data on a set of scales that might not match the scale of the data (that is, R's automatic rules might not work as I want).

```
## xlim, ylim set bounds: axes=FALSE turns off axes
plot(y~x,data=dd,xlim=c(200,800),ylim=c(200,800),axes=FALSE)
```

Now draw the axes manually:

```
ax <- seq(200,800,by=100) ## same for both axes
axis(side=1,at=ax) ## side=1 -> bottom
axis(side=2,at=ax) ## side=2 -> left
box() ## to draw the bounding box
```

In this example, all but one of the points in the data set are actually excluded from the plot: