# GP.conditional Input dimension mis-match

**URL:** <https://discourse.pymc.io/t/gp-conditional-input-dimension-mis-match/6766>\
**Category:** Questions\
**Created:** [February 15, 2021, 2:01pm UTC](https://discourse.pymc.io/t/gp-conditional-input-dimension-mis-match/6766 "2021-02-15T14:01:13Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![BrynWalton](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/brynwalton/32/3921_2.png) [@BrynWalton](https://discourse.pymc.io/u/BrynWalton)\
**Post date:** [February 15, 2021, 2:01pm UTC](https://discourse.pymc.io/t/gp-conditional-input-dimension-mis-match/6766/1 "2021-02-15T14:01:13Z")

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Hi, I’m new to PyMc3 and programming/gaussian processes in general. I’m trying to do a simple GP process on some 1D data (to start) using the following code and I’m getting an error that I just can’t fix and would really appreciate any ideas anyone might have.

It seems I can’t use the conditional method on a marginal gp model because the Xnew data is a different size to the X\_train data, but in the examples in the documentation it works fine?  
I don’t know how to enter the code and error in a nice way so I’m sorry for the screen shots.  
FYI it does not work with the # out ‘zero’ mean function either.

Thanks.

 ![image](https://canada1.discourse-cdn.com/flex036/uploads/pymc3/original/2X/a/a1df51e10e5a3e539713b36911ce32c5d1cc046b.jpeg)

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<div class="post-metadata">

**Author:** ![BrynWalton](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/brynwalton/32/3921_2.png) [@BrynWalton](https://discourse.pymc.io/u/BrynWalton)\
**Post date:** [February 15, 2021, 2:02pm UTC](https://discourse.pymc.io/t/gp-conditional-input-dimension-mis-match/6766/2 "2021-02-15T14:02:37Z")

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Here are the error images

 ![image](https://canada1.discourse-cdn.com/flex036/uploads/pymc3/original/2X/9/9ce2f45852de2667cca7ea8d2cf87ea5b34efdf1.jpeg)

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<div class="post-metadata">

**Author:** ![BrynWalton](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/brynwalton/32/3921_2.png) [@BrynWalton](https://discourse.pymc.io/u/BrynWalton)\
**Post date:** [February 15, 2021, 2:04pm UTC](https://discourse.pymc.io/t/gp-conditional-input-dimension-mis-match/6766/3 "2021-02-15T14:04:05Z")

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![image](https://canada1.discourse-cdn.com/flex036/uploads/pymc3/original/2X/b/b5e9048f76fdfb4070c190430a9b6a648ff0796c.jpeg)

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<div class="post-metadata">

**Author:** ![BrynWalton](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/brynwalton/32/3921_2.png) [@BrynWalton](https://discourse.pymc.io/u/BrynWalton)\
**Post date:** [February 15, 2021, 2:50pm UTC](https://discourse.pymc.io/t/gp-conditional-input-dimension-mis-match/6766/4 "2021-02-15T14:50:32Z")

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Ok, so I found the solution I think from another question by Ally-Lee. I think it’s because I made my y variable into column vectors as well as the X vectors like - y[:, None] when I should have just left it with dims (50, ). I still don’t understand why it was a problem but it seems to be working now so thanks to Ally and anyone who might want to offer an explanation.