LabVIEW
Home automated system question from a newbie
For the equation, all you need is an array of coefficient and polynomial evaluation. Look at the help.
You haven't included an image as promised, so we'll wait for that before giving more detailed advice. Actually, we would prefer a VI over an image any time.
As a "newbie", you must certainly have looked at the functions on the numeric palette, right? If you worked with pencil and paper, you might have figured out that you can write a function such as 114.91x^2 − 160.35x + 145.77 as ((114.91 * x) - 160.35) * x + 145.77 (taken from the last three terms of your expression -- the whole expression works the same way).
Since you are a beginner, "doing it by hand" in this manner isn't a bad idea, and gives you some experience with "wiring" (and, one hopes, striving for neatness in running the wires, which you do by "nudging" the functions around). You might noticed that there something of a pattern in the above code, and that you might be able to generalize this just by having an array of the coefficients and a single value for x, and might be able to write a function that does this for arbitrary polynomials of one variable, which is the LabVIEW function that Altenbach suggested to you. But learning to use the simple "math" functions and some wiring practice doesn't hurt, either.
Bob Schor
As I said, we can't really do much with pictures, but here are some comments:
- Your input array will eventually run out of elements and the total number of iterations is known before the loop starts. This means you should use a FOR loop. In you want to stop early, you can still show the conditional terminal wired to a stop button. Of course if the delay time for that iteration is very long, it might take a long time for the stop to apply. If this is a possibility, it might be better to use a while loop with a constant rate and go to the next point whenever time has elapsed. Make sure you encode a sentinel value at the end of the data array to stop the loop (e.g. wait=-1).
Here's how to do the polynomial (note that x can be an array of values, giving you the entire curve over the desired range if desired):
But of course you an also make your own. Same difference (There are quite a few other ways, e.g. look inside polynomial evaluation for an even simpler method). Make sure you fully understand how they work.:
Make sure your code is "scaleable" as these two examples. This mean there is no code change needed if you later need a different polynomial order. All you need to do is change the array size of coefficients and everything continues to work. Compare that with Bob's suggestion above where the code needs significant editing operations to change the order.
You were told in the other thread how to do a polynomial evaluation. Have you tried?
If you insist on using a formula node (makes no sense because there is no point to it!), you need to understand the formula. It is not e.g. "coefficientx5" but "coeficient times x to the power of five), etc.
Your formula node needs an input called x and you need to multiply each coefficient with the corresponding power of x.
