Julia LoadError: MethodError: no method matching

Question

I am getting an error while running the following Julia snippet

using GR, Interact
t = 0:0.01:1
@manipulate for phi=0:0.1:6.28
   plot(cos.(2π*t+phi))
end

LoadError: MethodError: no method matching +(::StepRangeLen{Float64,Base.TwicePrecision{Float64},Base.TwicePrecision{Float64}}, ::Float64)
Closest candidates are:
+(::Any, ::Any, !Matched::Any, !Matched::Any...) at operators.jl:529
+(!Matched::Bool, ::T<:AbstractFloat) where T<:AbstractFloat at bool.jl:104
+(!Matched::Float64, ::Float64) at float.jl:395
...
in expression starting at C:\Users\W.Aftab\Desktop\Julia_Codes\src\003.jl:3
(::getfield(Main, Symbol("##9#10")))(::Float64) at 003.jl:4
map(::Function, ::Widget{:slider,Float64}) at Observables.jl:174
top-level scope at manipulate.jl:25

Any idea what is wrong?

Answer 1

The following should work better:

using GR, Interact
t = 0:0.01:1
@manipulate for phi=0:0.1:6.28
   plot(cos.(2π*t.+phi)) #note the dot in ".+"
end

This is because in that expression, t is a range, and therefore 2pi*t is also a range, because in Julia the product between a scalar and a collection of value is defined to perform the product of each element of the collection by the scalar.

At each iteration in the loop, phi is a scalar. And the operation + is not defined between a scalar and a collection. It has to be explicitly broadcasted, for example using the .+ notation.