In my last post on engineering and whatnot, I commented on how to figure out how many stitches to add or subtract when trying to work beyond the range of given sizes in a pattern. Lynn raised a question on this topic: if the rate of change goes down and then back up, how do you know whether you should continue going up or go back down?
The answer probably isn’t as easy as any of us would like. You don’t.
My father taught college math until I was in junior high, and he used to talk to my brother and me about math whenever we went out to dinner. (I don’t know why the subject didn’t come up when we were having dinner at home, but virtually every time we went out for dinner, he’d pull his mechanical pencil out of his pocket and work us through math problems on paper napkins until our food arrived. And sometimes after.) When I was in fifth grade or so, I came home talking about interpolation and extrapolation. He drew me a graph with numbers on it and whatnot and asked me tell him what the Y-value of some number on the graph was. The answer was easy; it was right there on the graph. Then he asked me to give him the Y-value of a number not on the graph. That wasn’t so easy.
“Extrapolation is dangerous,” he said to me. “Just because this looks like a straight line between these two numbers doesn’t mean that it continues to behave like that beyond those points.”
This is a roundabout way of saying that you don’t really know how the pattern would behave beyond the range of sizes in the pattern. There are reasonable guesses, though. Patterns, unlike some math functions, tend to behave logically. In the example I gave in the last post, the trend would say either to decrease the rate of change by two or increase by two. That difference of four stitches could be tremendous, or it might not be, depending on your gauge. So yeah, some of it comes down to guesswork. If you want a tight fit, try going down. If not, go up. The nice thing about the guesswork here is that you’re really unlikely to mess something up irrevocably.
In other news, I finished my third of the baby sunhat in Holiday Knits. It’s such a sweet little pattern, and kind of unconventional for a knitted baby hat. Will have to get pictures of the second and third hats (the first has already been given away) tomorrow, along with an attempt at a ballet slipper for my former-ballerina-cousin’s baby girl (not sure if it’s working) and the baby blanket I’m blocking for my mom. I might post the pattern for it too, as it’s something we accidentally made up together.