在绘图中控制 xlim

Question

My example :

x = c(1:15)
y = c(-4:10)
plot(x, y)

R gives xlim automatically as : 2, 4, 6, ..., 14

How can I change it for : 1, 2, 3,..., 15

I've tried :

my.limits = as.numeric(seq(1, 15, by = 1))
x = c(1:15)
y = c(-4:10)
plot(x, y, ylim = c(-4,10), xlim = my.limits)

But with error :

Erreur dans plot.window(...) : valeur 'xlim' incorrecte

Answer 1

You can set the ticks manually like this:

x=c(1:15)
y=c(-4:10)
plot(x,y, xaxt="n", xlim = c(1,15)) 
axis(1, at = 1:15)

axt="n" omits drawing a x-axis in plot , first. axis manually draws it afterwards - you got more control this way.

Answer 2

Adding to lukeA's answer and using the my.limits sequence from your code:

# Tick marks every 1 unit:
my.limits = as.numeric(seq(1, 15, by = 1))
x=c(1:15)
y=c(-4:10)
plot(x,y, xaxt="n", xlim = c(1,15)) 
axis(1, at = my.limits)

# Tick marks every 5 units:
my.limits = as.numeric(seq(0, 100, by = 5))
x=c(1:100)
y=c(-49:50)
plot(x,y, xaxt="n", xlim = c(1,100)) 
axis(1, at = my.limits)