# Error in mul!(c,a,b) if size(b) = (n,1)

**URL:** <https://discourse.julialang.org/t/error-in-mul-c-a-b-if-size-b-n-1/47999>\
**Category:** General Usage\
**Created:** [October 8, 2020, 8:02pm UTC](https://discourse.julialang.org/t/error-in-mul-c-a-b-if-size-b-n-1/47999 "2020-10-08T20:02:41Z")\
**Posts on this page:** 1\
**Showing post:** 8

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**Author:** ![lmiq](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/lmiq/32/18314_2.png) [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Post date:** [October 9, 2020, 5:51pm UTC](https://discourse.julialang.org/t/error-in-mul-c-a-b-if-size-b-n-1/47999/8 "2020-10-09T17:51:09Z")

</div>

Yes, sure, here is a minimal example (with the only difference that the `y` data would be the data of my student):

```julia
julia> x = collect(1:10);

julia> y = rand(10,1);

julia> using LsqFit

julia> @. model(x, p) = p[1]*exp(-x*p[2])
model (generic function with 1 method)

julia> p0 = rand(2)
2-element Array{Float64,1}:
 0.4058105988552596
 0.5830419304135694

julia> fit = curve_fit(model, x, y, p0)
ERROR: MethodError: no method matching mul!(::Array{Float64,1}, ::LinearAlgebra.Transpose{Float64,Array{Float64,2}}, ::Array{Float64,2}, ::Bool, ::Bool)
Closest candidates are:

```

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