expression result must be of dimension 2 not 1

[pham5CDC]

when i want to use expression linear to scale composition flow slider of both channels extract from music,  how can i fix it

[Mylenium]

It means what it says. You might want to read up on expression basics. The immediate solution is simple:

mScale=linear(-your code here-)

[mScale, mScale]

Mylenium

[pham5CDC]

thank you so much i"ve fixed it

[Tomas Sinkunas · Accepted solution]

Basically, the scale property expects an array of 2 values - x and y, as in [x, y];

However, your slider returns only a single value, therefore AE throws an error. The easiest way to solve it would be to assign your slider value to some variable and then pass that variable twice as the result in the expression, similar to what @Mylenium has said. So something like this should do the trick:

let amp = linear(thisComp <... the rest of your slider expression ... >) ;
[amp, amp];