# \#variable-domains

**URL:** https://discuss.ampl.com/tag/variable-domains/48.md

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## [Is it necessary to apply normalization to unknown parameters with different scales?](https://discuss.ampl.com/t/is-it-necessary-to-apply-normalization-to-unknown-parameters-with-different-scales/1947)

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**Author:** [@ae.naderi](https://discuss.ampl.com/u/ae.naderi)\
**Replies:** 3\
**Last updated:** [October 22, 2024, 11:52pm UTC](https://discuss.ampl.com/t/is-it-necessary-to-apply-normalization-to-unknown-parameters-with-different-scales/1947 "2024-10-22T23:52:33Z")

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Hello everybody! I have a model built in AMPL. The scales of my unknown values are different. Two of them are coordinates, for the another; one has a scale between 2 and 9, and the other is between -150 and 50. I want …

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## [AMPL Modeling Tips #5: Non-contiguous variable domains](https://discuss.ampl.com/t/ampl-modeling-tips-5-non-contiguous-variable-domains/387)

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**Author:** [@fdabrandao](https://discuss.ampl.com/u/fdabrandao)\
**Replies:** 0\
**Last updated:** [February 20, 2023, 6:02pm UTC](https://discuss.ampl.com/t/ampl-modeling-tips-5-non-contiguous-variable-domains/387 "2023-02-20T18:02:05Z")

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Sometimes variable values are restricted to non-contiguous sets. Finite domain: var Buy {FOOD} in {0, 10, 30, 45, 55}; Finite domains as unions of integer sets: var Buy {FOOD} in 0..4 union 9..13 union 17..20; A …