Predict Example

[kikolobo]

Hello,

I am wondering what is the value of the variable X in the predict function? (The parameter we pass)..

Say I have 3 values pushed to the Average storage.

Lets say: 1, 2 and 4

And I want to predict what value comes next given this set. What should I pass as X or as predict parameter?

Thanks in advance.

[majenkotech]

Prediction uses the least squares function to make a y=mx+c representation of the data (a straight line). The X you pass is the X in that formula.

If you draw the data on a graph predict gives you the y value at point X on the graph.

[kikolobo]

Thank you for the prompt response.

So can we say X is a position in the internal array?

Normally X would be time in my application, but in this case there is no time reference in the internal storage, I am guessing a future index of the array is X for the prediction?

More concrete.. I am reading a load cell and I am getting KG 100 times per seconds. I am storing this value in Average library with push. The size of the storage is 100 slices.

I am trying to predict what weight will I get next given a linear action of adding weights to the cell?

Would X be 101? (If we have more than a 100 samples)?

[majenkotech]

X can be any value you want. If you have 100 data points then any value of X from 0 to 99 should give approximately the value in the array at that point. Any X bigger than 99 will be the value at that point in the future. Any X smaller than 0 will be the value at that point in the past.

At 100 samples per second an X in the order of 200 will be the estimated value one second in the future. An X of 100 will give you an estimated value for the next sample taken.

As I say the formula is y=mx+c which is a straight line graph:

So any point on the X axis below the size of your array (remember, arrays count from 0 not 1) should correspond to past data, and any point on the X axis equal to or greater than the size of your array will be an estimate of future values.