# Symbolics - Identity matrices for beginners

**URL:** <https://discourse.julialang.org/t/symbolics-identity-matrices-for-beginners/67391>\
**Category:** General Usage\
**Tags:** linearalgebra, symbolics\
**Created:** [August 31, 2021, 12:46am UTC](https://discourse.julialang.org/t/symbolics-identity-matrices-for-beginners/67391 "2021-08-31T00:46:45Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![banksiaboy](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/banksiaboy/32/27032_2.png) [@banksiaboy](https://discourse.julialang.org/u/banksiaboy)\
**Post date:** [August 31, 2021, 12:46am UTC](https://discourse.julialang.org/t/symbolics-identity-matrices-for-beginners/67391/1 "2021-08-31T00:46:45Z")

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Hi,  
I’m trying to relearn linear algebra for the basics of deep-learning. I also want to bootstrap myself into using Symbolics.jl at the same time. I used to enjoy owning [MuMath](https://en.wikipedia.org/wiki/MuMATH) back in the day.

I have basic 2 x 2 matrices hand-loaded with Symbolics variables, and they are multiplying, and displaying nicely.

I would like to know how to construct identity matrices in a conventional manner. I made a 2x2 Identity using `Matrix{Float64}(I,2,2)` This gives the appearance of working, but I don’t feel right about constraining the identity matrix to `Float64`.

How should I properly make a symbolic identity matrix?

 ![image](https://global.discourse-cdn.com/julialang/original/3X/d/6/d69dff4a52b6ea975e1f2b76b75cdd2ea35f3f34.png)

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**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [August 31, 2021, 1:05am UTC](https://discourse.julialang.org/t/symbolics-identity-matrices-for-beginners/67391/2 "2021-08-31T01:05:18Z")

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Why not just use `I`?

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<div class="post-metadata">

**Author:** ![banksiaboy](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/banksiaboy/32/27032_2.png) [@banksiaboy](https://discourse.julialang.org/u/banksiaboy)\
**Post date:** [August 31, 2021, 1:16am UTC](https://discourse.julialang.org/t/symbolics-identity-matrices-for-beginners/67391/3 "2021-08-31T01:16:26Z")

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Thanks Chris, I was hoping that would be the answer 🙂  
Ouch looking at my code - I was using `I` - didn’t use my subscript. The answer is I failed to find it by searching the documentation. It does appear in Pluto Live docs - once I knew what it was.  
What can I read to get a foundation in CA in the style of Symbolics?

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<div class="post-metadata">

**Author:** ![banksiaboy](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/banksiaboy/32/27032_2.png) [@banksiaboy](https://discourse.julialang.org/u/banksiaboy)\
**Post date:** [August 31, 2021, 1:21am UTC](https://discourse.julialang.org/t/symbolics-identity-matrices-for-beginners/67391/4 "2021-08-31T01:21:56Z")

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I’d like to not be more than 10% baffled by  
 ![image](https://global.discourse-cdn.com/julialang/original/3X/5/7/57d6a3f4889389fdf30909ef7b5a553121e93ca6.png)

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<div class="post-metadata">

**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [August 31, 2021, 2:14am UTC](https://discourse.julialang.org/t/symbolics-identity-matrices-for-beginners/67391/5 "2021-08-31T02:14:57Z")

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scalar `I` is equal to true. `*` must be doing the scalarized operation? That might be worth an issue.

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<div class="post-metadata">

**Author:** ![banksiaboy](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/banksiaboy/32/27032_2.png) [@banksiaboy](https://discourse.julialang.org/u/banksiaboy)\
**Post date:** [August 31, 2021, 4:50am UTC](https://discourse.julialang.org/t/symbolics-identity-matrices-for-beginners/67391/6 "2021-08-31T04:50:56Z")

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Issue #367