Thank you for the hint. But this means that I will still have missing responses in my data and this defeats my purpose to analyse the data using cluster analysis. 

 
Dr. Iasonas Lamprianou
Department of Social and Political Sciences
University of Cyprus


>________________________________
>From: Jim Lemon <jim@bitwrit.com.au>
>To: Iasonas Lamprianou <lamprianou@yahoo.com>
>Cc: "r-help@r-project.org" <r-help@r-project.org>
>Sent: Tuesday, 23 August 2011, 13:47
>Subject: Re: [R] likert scale analysis with R
>
>On 08/23/2011 08:39 PM, Iasonas Lamprianou wrote:
>>
>>
>> Dear colleagues,
>>
>>
>> I would like to run a cluster analysis on a number of variables. They are Likert Scale (0 to 10), but they also have a "Don't know' option at the end of the scale. Apparently, with the 'Don't Know' option in place, they cannot be considered to be linear or ordinal. How can these variables be analysed using R? One option would be to use poLC and treat them as categorical variables to classify the respondents into clusters (latent categorical variable). But is there a way to treat them as partly ordinal/conitinuous and partly categorical?
>>
>> Thank you
>> Jason
>>
>Hi Jason,
>The way I have treated this sort of response measure is to create two 
>variables, as two questions are being asked. One is:
>
>"Do you have an opinion on this statement?"
>
>and the other is:
>
>"How much do you agree or disagree with this statement?"
>
>(if the item really is a Likert scale). A "No" on the first question 
>automatically implies a missing value on the second.
>
>Oh, and I usually tell the person who has written the questionnaire to 
>limit each item to one question.
>
>Jim
>
>
>
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