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05-19-2016 02:44 AM

Dear Sir or Madam,

Can I please ask what do this errors mean? How can I resolve it? Thank you very much.

560 proc univariate data=temp; 561 var occ; 562 histogram / midpoints=0 to 600 by 50 563 lognormal 564 weibull 565 gamma; 566 inset n mean(5.3) std='Std Dev'(5.3) skewness(5.3) 567 / pos = ne header = 'Summary Statistics'; 578 run; NOTE: Since a threshold parameter (THETA) was not specified for the lognormal fit for occ, a zero threshold is assumed. ERROR: The smallest value of occ is less than or equal to the threshold parameter (THETA) for the lognormal fit. NOTE: The lognormal threshold parameter (THETA) must be less than 0. NOTE: The lognormal curve was not drawn because estimates could not be computed for all parameters. NOTE: Since a threshold parameter (THETA) was not specified for the Weibull fit for occ, a zero threshold is assumed. ERROR: The smallest value of occ is less than or equal to the threshold parameter (THETA) for the Weibull fit. NOTE: The Weibull threshold parameter (THETA) must be less than 0. NOTE: The Weibull curve was not drawn because estimates could not be computed for all parameters. NOTE: Since a threshold parameter (THETA) was not specified for the gamma fit for occ, a zero threshold is assumed. ERROR: The smallest value of occ is less than or equal to the threshold parameter (THETA) for the gamma fit. NOTE: The gamma threshold parameter (THETA) must be less than 0. NOTE: The gamma curve was not drawn because estimates could not be computed for all parameters. NOTE: At least one W.D format was too small for the number to be printed. The decimal may be shifted by the "BEST" format. NOTE: PROCEDURE UNIVARIATE used (Total process time): real time 0.19 seconds cpu time 0.04 seconds

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Posted in reply to wong

05-19-2016 05:49 AM

In three=parameter families that have a threshold parameters, the data must be strictly larger than the values of the threshold parameter. The reason is that the distributions you are fitting have a term that looks like

log( x[i] - theta )

or

(x[i] - theta)**c.

The LOG function is undefined when its argument is zero or negative. Similarly, the "raise to power function" is undefined for negative arguments when c is not an integer. (For example, c=1/2 is the square roo function.)

The most likely reason for these errors is that you have data values that are zero. Your choices include:

- Model the data by using different distributions
- Specify a value for the threshold parameters that is strictly less than the smallest data value
- Delete the bad data values if they are coding errors