Exec Error at line 343: log: FUNC SINGULAR: x = 0

GAMS
1

Dear GAMS Users,

I am trying to estimate some parameters.

using this equations:

obj1… sse1 =n= 0;
fit1(T1)… log(FOOD1(T1)) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));

It works fine. However when I extend the process to the whole data set, I get Exec Error at line 343: log: FUNC SINGULAR: x = 0

Therefore I introduce these conditions (trying with both gt0 and gt1) on my parameters

obj1… sse1 =n= 0;
fit1(T1)… log(FOOD1(T1)) $ (FOOD1(T1)and trend1(T1) and GDP1(T1) gt 0) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));


and it does not work.

Any idea about the proper way of treating this issue?

Thank you very much in advance!

Adriano

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2

Hello Adriano
I don’t know too much about Gams parameter estimation, bu to limit a variable (in your case a parameter to be estimated), you need to fix its lower bounds greater then zero:
FOOD1.lo(T1) = 0.0001;
trend1.lo(T1) = 0.0001;
GDP1.lo(T1) = 0.0001;
I hope I am right and it could help you.
Edson


2011/3/9 adriano spinelli

Dear GAMS Users,

I am trying to estimate some parameters.

using this equations:

obj1… sse1 =n= 0;
fit1(T1)… log(FOOD1(T1)) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));

It works fine. However when I extend the process to the whole data set, I get Exec Error at line 343: log: FUNC SINGULAR: x = 0

Therefore I introduce these conditions (trying with both gt0 and gt1) on my parameters

obj1… sse1 =n= 0;
fit1(T1)… log(FOOD1(T1)) $ (FOOD1(T1)and trend1(T1) and GDP1(T1) gt 0) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));


and it does not work.

Any idea about the proper way of treating this issue?

Thank you very much in advance!

Adriano

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Edson Valle
edsoncv@gmail.com

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3

Hi! trend1 and GDP1 are the model variables? If so, then you should apply a bound to these variables. In the blog http://yetanothermathprogrammingconsultant.blogspot.com/2009/05/domain-error-with-log.html are some way to fix the problem.

Hope this helps.

Regards,

Fabián

2011/3/9 adriano spinelli

Dear GAMS Users,

I am trying to estimate some parameters.

using this equations:

obj1… sse1 =n= 0;
fit1(T1)… log(FOOD1(T1)) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));

It works fine. However when I extend the process to the whole data set, I get Exec Error at line 343: log: FUNC SINGULAR: x = 0

Therefore I introduce these conditions (trying with both gt0 and gt1) on my parameters

obj1… sse1 =n= 0;
fit1(T1)… log(FOOD1(T1)) $ (FOOD1(T1)and trend1(T1) and GDP1(T1) gt 0) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));


and it does not work.

Any idea about the proper way of treating this issue?

Thank you very much in advance!

Adriano

–
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4

Reply-to: gamsworld@googlegroups.com

Edson and Fabian,

Thanks for your help and tips. Actually I solved the problem as follow:

fit1(T1)$(FOOD1(T1) and trend1(T1) and GDP1(T1))… log(FOOD1(T1)) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));
Best regards,
Adriano


2011/3/9 Fabián Mancilla

Hi! trend1 and GDP1 are the model variables? If so, then you should apply a bound to these variables. In the blog http://yetanothermathprogrammingconsultant.blogspot.com/2009/05/domain-error-with-log.html are some way to fix the problem.

Hope this helps.

Regards,

Fabián

2011/3/9 adriano spinelli

Dear GAMS Users,

I am trying to estimate some parameters.

using this equations:

obj1… sse1 =n= 0;
fit1(T1)… log(FOOD1(T1)) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));

It works fine. However when I extend the process to the whole data set, I get Exec Error at line 343: log: FUNC SINGULAR: x = 0

Therefore I introduce these conditions (trying with both gt0 and gt1) on my parameters

obj1… sse1 =n= 0;
fit1(T1)… log(FOOD1(T1)) $ (FOOD1(T1)and trend1(T1) and GDP1(T1) gt 0) =e= constant1 + tc1log(trend1(T1)) + income1log(GDP1(T1));


and it does not work.

Any idea about the proper way of treating this issue?

Thank you very much in advance!

Adriano

–
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To unsubscribe from this group, send email to gamsworld+unsubscribe@googlegroups.com.
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