A function to assess the variability in the area calculation

This function takes two profiles defined as (l1,z1) and (l2,z2) as inputs and calculates area between them

calc_var(dat, index, sigma_z, sigma_l)

Arguments

dat

data with all trapezoids information for area calculation
index

series identifier (1 or 2)
sigma_z

the uncertainty in measures l (can be different for the two series)

Value

var a table regarding the variance in areas calculated.