The best method to implement a way to find your (y) value based on the time (x value) is to write your data into an array. The data values will be organized chronologically into each of the array's elements. If the data points are equally spaced in time you will only need a one dimensional array. If the data points aren't equally spaced out, you will need to create a two dimensional array where the first row has information on the time each of these data points were acquired. The second row would consist of the data points.
Once you have your array, you can reference the values based on their time because you can use their element number (if you have a one dimensional array), or the time value(if you have a two dimensional array).
Santiago D
National Instruments
