Start or Stop expression at a given frame?

I can think of a way, but it may not be the most efficient way to do it.  I stink at expressions myself.   You can refer the wiggle values to a layer containing sliders.  Using hold keyframes, set the initial values.  At frame 100, change the slider values to turn the wiggle off.

Or just split the layer containing the wiggle at frame 100, and remove the wiggle expression.

You could use an if (time < a value) then.... but this gets very unweildly very quickly. As Dave said, the easiest thing to do is to split the layer.

Rick and Dave are correct that it may be easiest to split the layer, but there are examples in After Effects Help for doing this with expressions, here:

http://helpx.adobe.com/en/after-effects/using/expression-examples.html#expression_example_ start_or_stop_wiggle_at_specific_time

If you want it to hold the last wiggle value, I'd do it like this:

stopFrame = 100;

t = Math.min(time,framesToTime(stopFrame));

wiggle(3,10,1,.5,t)

Dan

If you are willing to purchase an additional extension, my Expression Timeline is a generic solution to limit expressions to a specific range, fade them in and out and even transition from one expression to another one.

Expression Timeline 2 - aescripts + aeplugins - aescripts.com

Add your wiggle

Create a new Null called "Control Layer"

To this add two Expression Control sliders, rename one "frequency" the other "amplitude"

Click on the padlock button in the effects Control panel to keep this visible for the next step

In the expression *** two new lines before wiggle and type;

f=

immediately drag the pickwhip from the expression to the "frequency" effect slider

add a semi colon after this

add a new line and type;

a=

immediately drag the pickwhip from the expression to the "amplitude" effect slider

add a semi colon after this

the next line should be your wiggle and it should read;

wiggle(f,a)

the entire expression should look something like this;

f=thisComp.layer("Controller").effect("frequency")("Slider");

a=thisComp.layer("Controller").effect("amplitude")("Slider");

w=wiggle(f,);

Now you have two sliders to control the frequency and amplitude of your expression

You can animate them to start and stop wherever you like

you can interpolate values or if you want values to suddenly change, Toggle Hold the keyframes

Here's a tutorial that will help you with this;

Setting variable wiggle values