Animation interface

[gdkrmr]

There is an issue with the current animation interface:

1. using Plots; anim = Animation() gives an error, shouldn't this initialize an empty animation object?
2. Something like this does not work:

plot()
anim = Animation()
for i in 1:0.1:π
    plot([sin,cos], 0, π)
    scatter!([i,i],[sin])
    frame(anim)
end
gif(anim)

An ugly workaround would be this:

plot()
anim = Animation()
for i in 0:0.1:π
    plot([sin,cos], 0, π)
    scatter!([i],[sin])
    scatter!([i],[cos])
    anim = Animation(current(),anim.dir,anim.frames)
    frame(anim)
end
gif(anim)

Here is what my intuition would expect: Animation should be mutable, so that anim.plt can be changed and frame() should always set anim.plt to current().

[tbreloff]

Your second example won't work. You're creating a new animation in each iteration. The first example should work fine. Are you on master? If not, I recommend a Pkg.checkout("Plots"). If it still doesn't work after a checkout let me know.

On Jan 11, 2016, at 3:42 AM, gdkrmr notifications@github.com wrote:

There is an issue with the current animation interface:
1 using Plots; anim = Animation() gives an error, shouldn't this initialize an empty animation object?
2 Something like this does not work:

plot()
anim = Animation()
for i in 1:01:π
plot([sin,cos], 0, π)
scatter!([i,i],[sin])
frame(anim)
end
gif(anim)
An ugly workaround would be this:

plot()
anim = Animation()
for i in 0:01:π
plot([sin,cos], 0, π)
scatter!([i],[sin])
scatter!([i],[cos])
anim = Animation(current(),animdir,animframes)
frame(anim)
end
gif(anim)
Here is what my intuition would expect: Animation should be mutable, so that animplt can be changed and frame() should always set animplt to current()

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[gdkrmr]

the second example is what actually works for me :-)
I have version 0.5.1

[tbreloff]

Ok I understand now why the second version works now, but both examples are very inefficient. Here's some pointers:

• plot or subplot will open up a brand new window/figure. This is not what you want... you really just want to update the data for one of the series
• Animation() should work fine if you checkout... there was a recent PR adding an empty constructor
• You can update just the underlying series data by indexing on the Plot object (i.e. getindex and setindex! are defined for the Plot)

So with those notes in mind, a better way to do what you're trying to do is this (which works for me):

using Plots
anim = Animation()
p = plot([sin,cos], 0, π, size=(300,300))
scatter!([0], [sin,cos])
for i in 0:0.1:π
    p[3] = [i], [sin(i)]
    p[4] = [i], [cos(i)]
    frame(anim)
end
gif(anim)

[gdkrmr]

ok, thanks, it works.
How would I reassign coordinates in scatter3d?

[tbreloff]

Sadly that's not implemented yet... an example placeholder is here: https://github.com/tbreloff/Plots.jl/blob/master/src/backends/pyplot.jl#L441-L444

[gdkrmr]

ok, thanks for the help.

[tbreloff]

I added a new macro: @animate (on dev branch). This allows for some boilerplate reduction. Here's a modification of the example above:

using Plots
pyplot(size=(300,200))
p = plot([sin,cos], 0, π, lab=[:sin :cos])
scatter!(1, lab="")
anim = @animate for x in 0:0.1:π
    p[3] = [x,x], [sin(x),cos(x)]
end
gif(anim)

[pkofod]

Can't get any easier than that!

[Evizero]

nice. I will try this soon

[pkofod]

It's nice that you can still frame(anim) if fps=1 is too fast.

[tbreloff]

@pkofod based on your wording, it seems like you might be confused on fps. It's frames per second, which is just how many of the calls to frame(anim) to fit into 1 second of real time (after the frames have been generated already).

However, if you really meant "I don't want to save a frame on each loop iteration"... I was thinking about adding some syntax to the macro, maybe like:

p = plot(1)
anim = @animate when(mod1(i, 3) == 1) for i=1:100
    push!(p, 1, rand())
end

and maybe the shorthand:

p = plot(1)
anim = @animate every(3) for i=1:100
    push!(p, 1, rand())
end

which would save a frame on every 3rd point added. It would expand to:

p = plot(1)
anim = begin
    anim = Animation()
    for i=1:100
        push!(p, 1, rand())
        if mod1(i, 3) == 1
            frame(anim)
        end
    end
    anim
end

Thoughts? Ideas for alternative syntax?

[pkofod]

@tbreloff , I was actually wrong and thought I was able to create two frames in a row, such that it would show two identical frames in a row (every frame is there twice, so with fps = 1 it would appear to have fps = 0.5 which is not possible as per your explanation), actually I was just able to write frame(anim) because anim was previously defined, but it did nothing (of course).

begin EDIT
So what I was looking for was a sort of repeat frame n times keyword, but apparently I was actually satisfied with fps=1, so...
end EDIT

I like both when for that general use and every for the case most would probably need.

[Evizero]

+1 for the macro suggestions

[tbreloff]

This is mostly done. I invite you to try it out on the dev branch. Here's the highlights:

A new macro @gif simplifies things more... choose from:

anim = @animate for i=1:10
  plot(rand(i))
end
gif(anim)

or

@gif for i=1:10
  plot(rand(i))
end

Keyword every followed by a positive integer after the for loop will only save only those frames. So "every 5" will save frames for loop iterations [1,6,11,...]:

@gif for i=1:10
  plot(rand(i))
end every 5

Keyword when followed by any valid boolean expression will only save a frame when the expression evaluates to true. A full example:

using Plots; pyplot(size=(300,200))
x = 0:0.1:2π
p = scatter(1, xlim=extrema(x), ylim=(-1,1))

@gif for xi in x
    push!(p, 1, xi, sin(xi))
end when abs(sin(xi))>0.2

Let me know what you think! (and if there are bugs, of course)

[Evizero]

Looks awesome. I will play with this

[pkofod]

👍 from here as well, I will play around with it some time next week.

[tbreloff]

I'm not sure why this is still open... I think the functionality is finished?