# Calculation of discriminant function scores from raw data

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## Calculation of discriminant function scores from raw data

 I’m interested in taking some data cases not used in the original DFA and “projecting” these into the DF space, using the coefficients from the SPSS output.  In this support doc:www.ibm.com/support/pages/which-coefficients-are-used-computing-discriminant-scores-spssit states that:"The raw or unstandardized canonical function coefficients are used to compute the saved or pinted discriminant function scores. The scores are computed by applying the regression-like equation of the constant plus each coefficient times the raw value of the appropriate variable, and summing.”I took the SPSS output table of Canonical Discriminant Function Coefficients (Unstandardized Coefficients) into Excel, along with the unstandardized original variables and tried to compute the scores of some observations used in the DFA, to make sure I was using the correct method before projecting in the new observations.   Basically just the regression equation:DFscore = v1*c1 + v2*c2 + v3*c3…. + constantThe scores I got were close to those saved from the analysis, but not the same.  They differed enough that I don’t think we are talking about rounding errors or something. Any advice or comment appreciated.Ian Martin===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
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## Re: Calculation of discriminant function scores from raw data

 If you are doing this within Statistics, the easiest way would be to save the discriminant model by exporting it to an XML file and then using the Utilities > Scoring Wizard to do the predictions.On Tue, Jan 14, 2020 at 11:45 AM Ian Martin <[hidden email]> wrote:I’m interested in taking some data cases not used in the original DFA and “projecting” these into the DF space, using the coefficients from the SPSS output.  In this support doc:www.ibm.com/support/pages/which-coefficients-are-used-computing-discriminant-scores-spssit states that:"The raw or unstandardized canonical function coefficients are used to compute the saved or pinted discriminant function scores. The scores are computed by applying the regression-like equation of the constant plus each coefficient times the raw value of the appropriate variable, and summing.”I took the SPSS output table of Canonical Discriminant Function Coefficients (Unstandardized Coefficients) into Excel, along with the unstandardized original variables and tried to compute the scores of some observations used in the DFA, to make sure I was using the correct method before projecting in the new observations.   Basically just the regression equation:DFscore = v1*c1 + v2*c2 + v3*c3…. + constantThe scores I got were close to those saved from the analysis, but not the same.  They differed enough that I don’t think we are talking about rounding errors or something. Any advice or comment appreciated.Ian Martin===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD -- Jon K Peck[hidden email] ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
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## Re: Calculation of discriminant function scores from raw data

 In reply to this post by Ian Martin-3 If you have the "old" (training)  dataset you can merge it with the new data points and rerun the analysis, now using the Selection Variable field. 14.01.2020 21:45, Ian Martin пишет: I’m interested in taking some data cases not used in the original DFA and “projecting” these into the DF space, using the coefficients from the SPSS output.   In this support doc: www.ibm.com/support/pages/which-coefficients-are-used-computing-discriminant-scores-spss it states that: "The raw or unstandardized canonical function coefficients are used to compute the saved or pinted discriminant function scores. The scores are computed by applying the regression-like equation of the constant plus each coefficient times the raw value of the appropriate variable, and summing.” I took the SPSS output table of Canonical Discriminant Function Coefficients (Unstandardized Coefficients) into Excel, along with the unstandardized original variables and tried to compute the scores of some observations used in the DFA, to make sure I was using the correct method before projecting in the new observations.   Basically just the regression equation: DFscore = v1*c1 + v2*c2 + v3*c3…. + constant The scores I got were close to those saved from the analysis, but not the same.  They differed enough that I don’t think we are talking about rounding errors or something.  Any advice or comment appreciated. Ian Martin ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
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## Re: Calculation of discriminant function scores from raw data

 In reply to this post by Ian Martin-3 Do you have the original dataset? If so, append the new cases to the old set. Create a value in the DFA grouping variable that is not in the original set of values. Then in then classification phase, treat that value as ungrouped. It is often useful to keep the original grouping variable and look at the assigned values vs the original values vs the assigned values of the ungrouped cases. Are the discriminating variables items from a summative scale? Does the output from the first DFA suggest items could be grouped int sets fro a summative scale score? ----- Art Kendall Social Research Consultants -- Sent from: http://spssx-discussion.1045642.n5.nabble.com/===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD Art Kendall Social Research Consultants