# Example 7.1: Create a Fibonacci sequence

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The Fibonacci numbers have many mathematical relationships and have been discovered repeatedly in nature. They are constructed as the sum of the previous two values, initialized with the values 1 and 1.**SAS and R**, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

A pdf of this example is available here.

**SAS**

In SAS, we use the

`lag`function (section 1.4.17, p. 22) to retrieve the last value.

data fibo; do i = 1 to 10; fib = sum(fib, lag(fib)); if i eq 1 then fib = 1; output; end; run; proc print data=fibo; run;

This generates the following output:

Obs i fib 1 1 1 2 2 1 3 3 2 4 4 3 5 5 5 6 6 8 7 7 13 8 8 21 9 9 34 10 10 55

**R**

In R we can loop over an array to perform the same job.

len <- 10 fibvals <- numeric(len) fibvals[1] <- 1 fibvals[2] <- 1 for (i in 3:len) { fibvals[i] <- fibvals[i-1]+fibvals[i-2] }

This generates the following output:

> fibvals [1] 1 1 2 3 5 8 13 21 34 55

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