# [rrd-users] Re: Quick RPN question... (Square root in RPN?)

Serge Maandag serge.maandag at staff.zeelandnet.nl
Tue Jun 10 10:18:47 MEST 2003

```rrdtool's log() might just be an oddly named ln().

Else you can convert by:

alog(b) = xlog(b) / xlog(a)

The symbol before log being the base number.

So ln(b) = log (b) / log (2)

Sqrt(x) = exp(ln(x)/2) would become Sqrt(x) = exp( (log(x)/log(2)) /2)

Serge.

-----Original Message-----
From: Simon Mullis [mailto:Simon.Mullis at equinoxsolutions.com]
Sent: Monday, June 09, 2003 4:49 PM
To: 'Alex van den Bogaerdt'; RRD Users
Subject: [rrd-users] Re: Quick RPN question... (Square root in RPN?)

Alex,

Thanks for the idea - That works with natural log:

i.e. Sqrt(x) = exp(ln(x)/2)

Do we have ln in our RPN implementation?  I'm not sure that we do?!!

Thanks

SM

-----Original Message-----
From: Alex van den Bogaerdt [mailto:alex at ergens.op.het.net]
Sent: 09 June 2003 12:29
To: RRD Users
Subject: [rrd-users] Re: Quick RPN question... (Square root in RPN?)

On Mon, Jun 09, 2003 at 11:07:40AM +0100, Simon Mullis wrote:
> Hello all,
>
> Am I right in thinking there is no easy way to do a square root in
RPN?

Isn't a square root the same as exp(log(x)/2) ?

CDEF:y=x,LOG,2,/,EXP

Not sure,never tried it, just try it yourself.

HTH
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