Tutorial :Including variables in expression call in R



Question:

I was wondering if it were possible to include variables when using expression in R.

For instance I would like to do something like this:

par(mfrow=c(2,3))  for (i in 1:6)      {      plot(x, p1-i*p2, main=expression(Phi[1] - i * Phi[2]))      }  

But this does not work, as it prints Φ1 - iΦ2 (i.e. it does not substitute i with 1, 2, ... 6


Solution:1

Use substitute:

> substitute(Phi[1] - i* Phi[2], list(i = i))  Phi[1] - 3 * Phi[2]  


Solution:2

Looks like it uses the variables. I set x = 1 and used the following.

> p1 = 100  > p2 = 10  > for (i in 1:6)  +     {  +     plot(x, p1-i*p2, main=expression(Phi[1] - i * Phi[2]))  +     }  >   

It gave me 6 graphs for Φ1 - iΦ2 with each showing the Y value descending.


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