help with statistics in R - how to measure the effect of users in groups

Thanks Petr. I will try it on the real data.

But that will only show that the groups are different or not.
Is there any way I can test if the users are different when they are in 
different groups? 

Regards
Gawesh

On Mon, Oct 10, 2011 at 11:17 AM, Petr PIKAL <petr.pikal at precheza.cz> 

Hi Petr,

It's not an equation. It's my mistake; the * are meant to be field
separators for the example data. I should have just use blank spaces 

follows:

users   Group1   Group2   Group3
u1        10           5            N/A
u2         6          N/A          4
u3         5           2            3


Regards
Gawesh

OK. You shall transform your data to long format to use lm

test <- read.table("clipboard", header=T, na.strings="N/A")
test.m<-melt(test)
Using users as id variables
fit<-lm(value~variable, data=test.m)
summary(fit)

Call:
lm(formula = value ~ variable, data = test.m)

Residuals:
  1    2    3    4    6    8    9
 3.0 -1.0 -2.0  1.5 -1.5  0.5 -0.5

Coefficients:
              Estimate Std. Error t value Pr(>|t|)
(Intercept)       7.000      1.258   5.563 0.00511 **
variableGroup2   -3.500      1.990  -1.759 0.15336
variableGroup3   -3.500      1.990  -1.759 0.15336
---
Signif. codes:  0 ?***? 0.001 ?**? 0.01 ?*? 0.05 ?.? 0.1 ? ? 1

Residual standard error: 2.179 on 4 degrees of freedom
 (2 observations deleted due to missingness)
Multiple R-squared: 0.525,      Adjusted R-squared: 0.2875
F-statistic: 2.211 on 2 and 4 DF,  p-value: 0.2256

No difference among groups, but I am not sure if this is the correct way
to evaluate.

library(ggplot2)
p<-ggplot(test.m, aes(x=variable, y=value, colour=users))
p+geom_point()

There is some sign that user3 has lowest value in each group. However 

including users to fit there is not enough data.

Regards
Petr

On Mon, Oct 10, 2011 at 9:32 AM, Petr PIKAL <petr.pikal at precheza.cz>

wrote:

Hi

I do not understand much about your equations. I think you shall 

to

Practical Regression and Anova Using R from J.Faraway.

Having data frame DF with columns - users, groups, results you could

do

fit <- lm(results~groups, data = DF)

Regards
Petr

Hi,

I'm a newbie to R. My knowledge of statistics is mostly 

My

problem is how to measure the effect of users in groups. I can

calculate

a

particular attribute for a user in a group. But my hypothesis is

that

the

user's attribute is not independent of each other and that the

user's

attribute depends on the group ie that user's behaviour change 

on

the

group.

Let me give an example:

users*Group 1*Group 2*Group 3
u1*10*5*n/a
u2*6*n/a*4
u3*5*2*3

For example, I want to be able to prove that u1 behaviour is

different

in

group 1 than other groups and the particular thing about Group 1 

that

users in Group 1 tend to have a higher value of the attribute 

measurement.


Hence, can use R to test my hypothesis. I'm willing to learn; so 

this

is

very simple, just point me in the direction of any online 

about

it. At the moment, I don't even how to define these class of

problems?

That

will be a start.

Regards
Gawesh

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