> On Jul 7, 2016, at 3:36 PM, Jim Lemon <drjimle...@gmail.com> wrote:
>
> Hi Cristina,
> Try this:
>
> names(mydata)
>
> It may be NULL or "ppitrst" may be absent.
I've already suggested to Christina that she make sure the variables are
spelled correctly and she reports they are all present in her dataset. So I
tried a formula such as she posed with '1' added to each variable and this does
throw the same error with the 'values'-dataframe that is used in the examples
for that package.
> data(values,package='poLCA')
> str(values)
'data.frame': 216 obs. of 4 variables:
$ A: num 2 2 2 2 2 2 2 2 2 2 ...
$ B: num 2 2 2 2 2 2 2 2 2 2 ...
$ C: num 2 2 2 2 2 2 2 2 2 2 ...
$ D: num 2 2 2 2 2 2 2 2 2 2 ...
> library(poLCA)
Loading required package: scatterplot3d
Loading required package: MASS
> poLCA( cbind(A+1,B+1) ~ C, data=values)
Error in `[.data.frame`(data, , match(colnames(y), colnames(data))[j]) :
undefined columns selected
So I then tried removeing those "+1`"'s (which didn't seem to have much
justification):
> poLCA( cbind(A,B) ~ C, data=values)
Conditional item response (column) probabilities,
by outcome variable, for each class (row)
$A
Pr(1) Pr(2)
class 1: 0.3428 0.6572
class 2: 0.0307 0.9693
$B
Pr(1) Pr(2)
class 1: 0.7737 0.2263
class 2: 0.1386 0.8614
snipped the rest of the output.
So "why add 1?" Seems to disturb the functions formula processing logic and is
so far not explained.
--
David.
>
> Jim
>
>
> On Thu, Jul 7, 2016 at 8:26 PM, Cristina Cametti
> <cristina.came...@gmail.com> wrote:
>> Dear all,
>>
>> I am not able to find a reliable r code to run a multilevel latent class
>> model. Indeed, I have to analyze how social trust (three variables form the
>> ESS survey) might vary between countries (21 countries in my database). I
>> tried to use the poLCA package but I am not sure if my code is right. This
>> is my code:
>> lca <- cbind(ppltrst+1,pplfair+1,pplhlp+1)~cntry
>> lc <- poLCA(lca,mydata)
>>
>> However, I get an error message:
>> Error in `[.data.frame`(data, , match(colnames(y), colnames(data))[j]) :
>> undefined columns selected
>>
>> How can I solve this? Is the code completely wrong or I missed some passages?
>> Thank you very much for your help!
>>
>> Cristina
>> [[alternative HTML version deleted]]
>>
David Winsemius
Alameda, CA, USA
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