Message-ID: <F9D87BFC-3548-43BF-B841-3BC10EE6DA9E@comcast.net>
Date: 2010-01-01T22:03:15Z
From: David Winsemius
Subject: need more help.... Re: iterating over a data frame the R way?
In-Reply-To: <7642E99C-75AD-4815-92C0-7EBD9779D968@me.com>
On Jan 1, 2010, at 11:20 AM, donahchoo at me.com wrote:
> Okay, I don't know if I'm blocking because of my other programming
> language experience of if I'm just being dense.
>
> I have a data.frame with high,open,low,last,day, and start_time time
> columns. What I want to do is get all the rows with the same day
> and process each of those columns.
The usual method of doing that sort of operation the application of a
function within categories using tapply. See the examples in:
?tapply
> If I was able to run a query against the data.frame I would be want
> something like:
>
> result = all the rows where the day is equal to 2007-12-05
>
> Then I would want get max(result["high"]), min(result["low"])
>
> How do I do this? I tired sqldf, but its complaining about
> libtcl0.5.8 not being found. I'm on OS X 10.5.8 and haven't yet
> tired to install a new version of tcl in /usr/local.
>
> Here's the dataframe:
Nope... nothing came through. Read the posting guide for the proper
way to either include r objects in an email or to attache txt files.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT