From: Vadim Ogranovich <vogranovich_at_jumptrading.com>

Date: Thu, 03 May 2007 07:57:45 -0500 (CDT)

R-help_at_stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Thu 03 May 2007 - 13:08:18 GMT

Date: Thu, 03 May 2007 07:57:45 -0500 (CDT)

Hi,

I ran into a problem of converting a text representation of an expression into parsed expression to be further evaluated inside lm ().

*> n <- 100
**> data <- data.frame(x= rnorm (n), y= rnorm (n))
**> data. lm <- lm (y ~ x, data=data)
**>
*

> ## this works

> update(data. lm , subset=x<0)

Call:

lm (formula = y ~ x, data = data, subset = x < 0)

Coefficients:

(Intercept) x

-0.07864094193322170023 -0.14596982635007796358

*>
**> ## this doesn't work
**> ## text representation of subset
*

> subset <- "x<0"

> update(data. lm , subset=parse(text=subset))

Error in `[.data.frame`(list(y = c(-0.601925958140825, -0.111931189071517, :
invalid subscript type

What is the correct way to convert "x<0" into a valid subset argument?

Thanks,

Vadim

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