I have a function that takes fixed input arrays and variable scalars to produce a scalar return value. I would like to use the broadcast capability of Julia to turn the variable scalars into arrays, and have it return an array of the same size. Is there a straightforward way to get the broadcast sy…

You can turn one of the arguments into a tuple to consider it as a scalar: For example (if I understood your question correctly): f(x,y) = sum(x) + y f([1,2,3], 4) #-> 10 f([1,2,3], 5) #-> 11 f.([1,2,3], [4,5]) # -> error f.(([1,2,3],), [4,5]) # -> [10, 11] # this works …

Also see this (ongoing) discussion: [image] recent broadcast changes (iterate by default), scalar struct, and `@.` Internals & Design The current broadcasting behavior is non-intuitive when used with @. Julia Version 0.7.0-DEV.5222, Commit 7144b6b816 (2018-05-25 20:23 U…

[image] ffevotte: You can turn one of the arguments into a tuple to consider it as a scalar: Wrapping an argument in Ref(x) also works and is a common idiom for this.

If you want to override the broadcasting behaviour for a particular function, it’s possible by adding a new method to the broadcasted function. However, I’m not sure it’s a particularly advisable thing to do since your function will behave differently to most other functions. julia> _f(x,y) = sum(x…

The tuple-wrapping trick seems to work with Julia v0.7. I didn’t have success with the Ref() trick - will need to experiment further. Thanks!

[image] ronubi: I didn’t have success with the Ref() trick - will need to experiment further. It is not a “trick”, but part of the semantics of broadcasting . If it does not work, that is a bug, so please provide a self-contained MWE that demonstrates this.

This doesn’t seem to work, as of Julia 1.7. Has it been replaced/deprecated?

It should work. Can you provide a minimal example?

f(x,y)=2*x+3*y then julia> f.(([1,2]),[3,4,5]) ERROR: DimensionMismatch("arrays could not be broadcast to a common size; got a dimension with lengths 2 and 3") Stacktrace: [1] _bcs1 @ ./broadcast.jl:516 [inlined] [2] _bcs @ ./broadcast.jl:510 [inlined] [3] broadcast_shape @ ./broadcast…

Hi Sorry - I tried Ref() again and it worked [sorry - I thought I had tried it before, but something must have been different]

How to broadcast over only certain function arguments?

General Usage

ffevotte January 4, 2019, 4:39pm 3

Also see this (ongoing) discussion:

Topic		Replies	Views
Broadcasting a function with some non-broadcasted inputs General Usage	4	691	December 20, 2018
How to vectorize only one argument in function call General Usage question , broadcasting	8	1806	September 5, 2022
What's the "right" way to broadcast vector-valued functions? New to Julia broadcast , array	4	1651	November 6, 2019
Providing hints to broadcast? New to Julia	8	546	August 28, 2019
Broadcasting a scalar New to Julia broadcast	4	1123	May 8, 2017

How to broadcast over only certain function arguments?

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