Re: st: CR and AVE for factor analysis with 2 factors

["Florian Christian Esser" <florian.esser@tu-dortmund.de>]

Here we go (I included the uniqueness and the loadings as well).
Communalities are on the bottom:
_____________________________________________________________


. matrix list e(Psi)

e(Psi)[1,6]
            zwmdiff_1  zwpdiff_1  zwpdiff_2   zwcost_1   zwcost_2   zwcost_3
Uniqueness  .14721836  .16061008  .12541414  .01425274  .01366305  .02630422

. matrix list e(L)

e(L)[6,3]
              Factor1     Factor2     Factor3
zwmdiff_1   .81629684     .233233   .36337787
zwpdiff_1   .82275816   .39938175  -.05434294
zwpdiff_2    .8671496   .34761446   .04244559
 zwcost_1  -.52875169   .83417333   .10160593
 zwcost_2  -.51348298   .84223386   .11538764
 zwcost_3  -.18959666  -.28021389    .9269461

. matrix psi = e(Psi)'

. matrix communalities = J(rowsof(psi),1,1)

. matrix communalities = communalities - psi

. matrix colnames communalities = communalities

. matrix list communalities

communalities[6,1]
           communalit~s
zwmdiff_1     .85278164
zwpdiff_1     .83938992
zwpdiff_2     .87458586
 zwcost_1     .98574726
 zwcost_2     .98633695
 zwcost_3     .97369578
_____________________________________________________

> What is implied by your log is that
>
> replace sum_factors = sum_factors + sqrt(communalities[3,1])
>
> has the effect of replacing -sum_factors- with missing. So, please
> show us that -communalities- matrix,
> namely the result of your line
>
> matrix list communalities
>
> (I see on closer examination that the -communalities- matrix is not
> the communalaties as first reported, but modified.)
>
> No idea, sorry, about your general factor analysis question. I'm
> firmly a PCA person.
> Nick
> njcoxstata@gmail.com
>
>
> On 29 October 2013 07:14, Florian Christian Esser
> <florian.esser@tu-dortmund.de> wrote:
>> Hi Nick, thanks a lot for your advice.
>> Unfortunately, all my communalities are positive.
>> Does anyone have any ideas, what else could cause the issue?
>>
>> Is the general approach correct, to calculate CR and AVE for both
>> factors
>> at the same time, or would I have to do it individually. I.e. I do the
>> factor analysis, identify, that the indicators load on two factors and
>> then calculate CR and AVE for each factor individually?
>>
>>> Your missing value is presumably the result of taking the square root
>>> of a negative number. Is at least one of your communalities reported
>>> as negative?
>>>
>>> That aside you have segments like
>>>
>>> gen nvar = e(df_m)
>>> gen sum_factors=0
>>> local i=1
>>> while `i' <= nvar {
>>> replace sum_factors = sum_factors + sqrt(communalities[`i',1])
>>> local i=`i'+1
>>> }
>>>
>>> You can simplify this. First, to hold constants, use locals or
>>> scalars, not variables. Second, use -forval- to loop here:
>>>
>>> local nvar = e(df_m)
>>> local sum_factors = 0
>>> forval i = 1/`nvar' {
>>>      local sum_factors = `sum_factors'  + sqrt(communalities[`i',1]
>>> }
>>>
>>> Third, use Mata instead. Here is a self-contained example:
>>>
>>> . matrix foo = (1,2,3,4)
>>>
>>> . mata : st_numscalar("sum_factors", sum(sqrt(st_matrix("foo"))))
>>>
>>> . scalar li
>>> sum_factors =  6.1462644
>>>
>>> However, none of these tricks can get round what appears to be your
>>> problem.
>>>
>>>
>>> Nick
>>> njcoxstata@gmail.com
>>>
>>>
>>> On 28 October 2013 14:11, Florian Christian Esser
>>> <florian.esser@tu-dortmund.de> wrote:
>>>> Hi everyone,
>>>>
>>>> I am trying to do factor analysis in order to measure two strategy
>>>> constructs. I have 6 indicators that load on these two constructs. Now
>>>> I
>>>> want to calculate composite reliability (CR) and average variance
>>>> extracted(AVE).
>>>> I use the following code (here for CR):
>>>> ___________________________________________________________________
>>>> factor zwmdiff_1 zwpdiff_1 zwpdiff_2 zwcost_1 zwcost_2 zwcost_3, pcf
>>>> matrix list e(Psi)
>>>> matrix list e(L)
>>>> matrix psi = e(Psi)'
>>>> matrix communalities = J(rowsof(psi),1,1)
>>>> matrix communalities = communalities - psi
>>>> matrix colnames communalities = communalities
>>>> matrix list communalities
>>>> gen nvar = e(df_m)
>>>> gen sum_factors=0
>>>> local i=1
>>>> while `i' <= nvar {
>>>> replace sum_factors = sum_factors + sqrt(communalities[`i',1])
>>>> local i=`i'+1
>>>> }
>>>> generate sum_psi=0
>>>> local i=1
>>>> while `i' <= nvar {
>>>> replace sum_psi = sum_psi + psi[`i',1]
>>>> local i=`i'+1
>>>> }
>>>> gen cr=(sum_factors*sum_factors)/((sum_factors*sum_factors)+sum_psi)
>>>> drop nvar
>>>> drop sum_factors
>>>> drop sum_psi
>>>> list cr in 1
>>>> _________________________________________________________________
>>>>
>>>> The problem is that once the local macro starts running it tells me:
>>>> _____________________________
>>>> [...]
>>>> (534 real changes made)
>>>> (534 real changes made)
>>>> (534 real changes made, 534 to missing)
>>>> (0 real changes made)
>>>> (0 real changes made)
>>>> (0 real changes made)
>>>> [...]
>>>> ___________________________
>>>>
>>>> and accordingly there is an empty result for CR.
>>>> If I add "factors(1)" in the command line above, I get a result, but I
>>>> since I have two factors, I think it is not correct to do this.
>>>>
>>>> Does anyone know what to do here?
>>>>
>>>> Thanks a lot in advance.
>>>>
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>>
>>
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