R: using `rnorm` to create vectors with specific variance

Question

I want to create two different vectors of data which are normal distributions. One which has a a mean value of 0 and variance of 1; one which has a mean value of 0 and variance of 0.25.

Can this be done with rnorm? If not what is the best way to do this in R?

score 1 · Accepted Answer · answered Oct 30 '16 at 12:44

1

Of course. Type ?rnorm into the console to learn more about it. I'm assuming you want vectors with 100 numbers, but just change n if you want.

vector1 = rnorm(n = 100, mean = 0, sd = sqrt(1))
vector2 = rnorm(n = 100, mean = 0, sd = sqrt(0.25))

answered Oct 30 '16 at 12:44

CephBirk

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Sorry this is so ridiculously obvious now. I just couldn't understand why you could only set the mean and the SD but nor the var. – RDJ Oct 30 '16 at 12:47
2

No problem. We all have those moments :) – CephBirk Oct 30 '16 at 12:52

score 1 · Answer 2 · answered Oct 30 '16 at 12:45

yes you can do it with rnorm()

first vector( of 1000 elements) with mean = 0 and variance = 1( std.dev = 1)

a = rnorm(1000, mean = 0, sd = 1)

second vector ( of 1000 elements) with mean = 0 and variance = 0.25( std.dev = 0.5)

b = rnorm(1000, mean = 0, sd = 0.5)

R: using `rnorm` to create vectors with specific variance

2 Answers2