Ah I think I should have maybe phrased the question differently.

Due to the high amount of variance in my data set, I need for the slopes to be calculated from the entire range of data - essentially I want to see the same values as if you were going to to a linear fit line and read off the x coefficient from that. Otherwise if the particular day is extremely high or low, it might give erroneous results. Is there anyway to make that calculation in the way I am asking?