# Jacobian matrix

**URL:** <https://discourse.julialang.org/t/jacobian-matrix/75117>\
**Category:** New to Julia\
**Created:** [January 24, 2022, 1:08pm UTC](https://discourse.julialang.org/t/jacobian-matrix/75117 "2022-01-24T13:08:36Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![pcmk1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pcmk1/32/33110_2.png) [@pcmk1](https://discourse.julialang.org/u/pcmk1)\
**Post date:** [January 24, 2022, 1:08pm UTC](https://discourse.julialang.org/t/jacobian-matrix/75117/1 "2022-01-24T13:08:36Z")

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![캡처](https://global.discourse-cdn.com/julialang/original/3X/1/2/12eb30d3ff2a10ccab72862f0bbd5069887085e5.png)  
I calculated the Jacobian matrix. I guess one of the line should be full of -0.97 since one of the function is 29.927071171061 - 0.97\*t and the derivative of it is just -0.97. But only one element of the Jacobian matrix has a value of -0.97. Could you explain why?

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**Author:** ![trahflow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/trahflow/32/30585_2.png) [@trahflow](https://discourse.julialang.org/u/trahflow)\
**Post date:** [January 24, 2022, 1:54pm UTC](https://discourse.julialang.org/t/jacobian-matrix/75117/2 "2022-01-24T13:54:12Z")

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Welcome 🙂

Are you aware that you put a 5x5 rank-1 matrix as the first argument into your function `FOCs`?  
`[t t t t t]` where `t = ss_vec` does give you just that. If that’s what you actually meant, I think the answer depends on the actual definition of `FOCs`

(note that a minimal working example that can be _copy-pasted_ would make it a lot easier for people to help you. Please look also here for some other recommendations: [Please read: make it easier to help you](https://discourse.julialang.org/t/please-read-make-it-easier-to-help-you/14757))