Can I use do loop to calculation pi?

[yuwentaiwan]

I   fi       pi(=( f(i)+f(i-1) ) /2 )

1  0.263    (0.263+0)/2                (f(0)=0)

2  0.263    (0.263+0.263)/2

3  0.91     (0.91+0.263)/2

4  0.12     (0.12+0.91)/2

5  0.12     (0.12+0.12)/2

Can I use do loop or other method to calculation pi?

Thanks!

[Jagadishkatam]

I believe you can achieve the same result without the do loop if you prefer it this way

data have;
input f;
cards;
0.263 
0.263 
0.91  
0.12  
0.12
;
  
data want;
set have;
pi=((f+coalesce(lag(f),0))/2);
run;

[ed_sas_member]

Hi @yuwentaiwan 

You can use the LAG() function to retrieve the previous value of fi.

The SUM() function is better than the "+" operator in your case as it ignores missing values. So it can easily handle the calculation at the first row, where lag(i) is not defined.

Best,

data want;
	set have;
	pi = sum(fi,lag(fi))/2;
run;

[ballardw]

---

@yuwentaiwan wrote:

I   fi       pi(=( f(i)+f(i-1) ) /2 )

1  0.263    (0.263+0)/2                (f(0)=0)

2  0.263    (0.263+0.263)/2

3  0.91     (0.91+0.263)/2

4  0.12     (0.12+0.91)/2

5  0.12     (0.12+0.12)/2

Can I use do loop or other method to calculation pi?

Thanks!

---

Is this a programming exercise or do you want to USE the value of pi?

If you need to use pi then you would use the function CONSTANT with 'pi' as the argument.

data junk;
   x=constant('pi');
   put x best16.;
run;

[RichardDeVen]

You can use Proc DS2 or FCMP to compute via recursion.

Or try Proc FCMP SOLVE() function