linear model lme4

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No, as the error states, you need random effects in lmer. But, you don't for lm() and that is what you're running with no random effects. However, some caution is warranted on the comparison.
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Brian Smith
Sent: Friday, February 25, 2011 10:06 AM
To: r-help at r-project.org
Subject: [R] linear model lme4

Hi,

I wanted to check the difference in results (using lme4) , if I treated a
particular variable (beadchip) as a random effect vs if I treated it as a
fixed effect.

For the first case, my formula is:

lmer.result <- lmer(expression ~ cancerClass + (1|beadchip))

For the second case, I want to do:

lmer.result2 <- lmer(expression ~ cancerClass + beadchip)

However, I get an error in the second case:

Error in lmerFactorList(formula, fr, 0L, 0L):
  No random effects terms specified in formula

Is there any way that I can get lmer() to accept a formula without a random
effect?

many thanks

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