Well, now you have one.
I am a bit surprised that even in this thread it took so long to come to something that I thought had to be of common knowledge to experienced users.
. in MAYA there is a good attribute in the render settings called “by frame” - it renders just the second, third, fourth, etc. frame of an animation WITHOUT changing the basic animation. so…
by frame = 1 - every frame
by frame = 2 - every 2nd frame
by frame = 3 - every 3rd frame
Well, it has the advantage of being simpler to understand but, by the look of it, it is definitely less powerful than the Blender mapping feature.
For example, how could you use your ‘by frame’ command to accelerate the anim by 2.45 for example? In Blender all there is to do is to divide the default ‘Map New’ value of 100 by the accelerating factor of 2.45 (IOW enter the expression ‘100/2.45’ in the ‘Map New’ field). Unless one want a pause at the end of the anim, the number of frames should be divided by the same factor.
To slow down the anim OTOH one just has to multiply the ‘Map New’ default value of 100 by the right factor. Want 5.34 times slower? Just multiply ‘Map New’ by 5.34. Likely you’ll want to increase the number of frames by the same factor.
NOTE: Blender seems to drop the decimal part in fields that usually are set by whole numbers. I cannot tell if, internally, the decimal fraction is taken into account. If not the mapping is not all that precise but precision should be enough for most, if not just any, uses.