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Vu Xing
Vu Xing
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I fitted a generalized additive model (GAM) using SAS PROC GAMPL with a Poisson distribution and a log link function.

The outcome was a measure of repair cost for a large collection of units (4k+). There is a percentage of units with zero values that are zero ($0) which I expected to simply drop out of the model estimation process due to the log transformation. However, the reported totals for the used observations do not reflect this.

The units with zero values are included in the input because I'm using the GAM model for predictions and I need predictions for the entire collection of units.

Are these observations really being used? If so, does anyone know how?

Thanks

I fitted a generalized additive model (GAM) using SAS PROC GAMPL with a Poisson distribution and a log link function.

The outcome was a measure of repair cost for a large collection of units (4k+). There is a percentage of units with zero values which I expected to simply drop out of the model estimation process due to the log transformation. However, the reported totals for the used observations do not reflect this.

The units with zero values are included in the input because I'm using the GAM model for predictions and I need predictions for the entire collection of units.

Are these observations really being used? If so, does anyone know how?

Thanks

I fitted a generalized additive model (GAM) using SAS PROC GAMPL with a Poisson distribution and a log link function.

The outcome was a measure of repair cost for a large collection of units (4k+). There is a percentage of units with values that are zero ($0) which I expected to simply drop out of the model estimation process due to the log transformation. However, the reported totals for the used observations do not reflect this.

Are these observations really being used? If so, does anyone know how?

Thanks

Source Link
Vu Xing
Vu Xing
  • 3
  • 3

What happens to zero values during statistical model estimation with a log link function? (SAS PROC GAMPL - GAM)

I fitted a generalized additive model (GAM) using SAS PROC GAMPL with a Poisson distribution and a log link function.

The outcome was a measure of repair cost for a large collection of units (4k+). There is a percentage of units with zero values which I expected to simply drop out of the model estimation process due to the log transformation. However, the reported totals for the used observations do not reflect this.

The units with zero values are included in the input because I'm using the GAM model for predictions and I need predictions for the entire collection of units.

Are these observations really being used? If so, does anyone know how?

Thanks