source("http://macosa.dima.unige.it/r.R") # If I have not already loaded the library ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- S 06 To estimate the best fit straight line Straight line that crosses exactly (A,B) and fits some points that have x and y coordinates with ex and ey precisions. Command: pointDiff(A,B, x,y, ex,ey) pointDiff2(A,B, x,y, ex,ey) produces outputs in fractional form Instead, if I use the following command I represent points without curves that approximate them. pointDiff0(x,y, ex,ey) # I can change color to the rectangles that represent points with colRect command. # What can I say about the linear function F such that F(5) = 10 whose graph passes # through: # x: 12±1 17±1 24±1 33±1.5 # y: 18±2 27±2 31±2.5 45±3 Plane(0,35, 0,50) x = c(12, 17, 24, 33); ex = c(1, 1, 1, 1.5) y = c(18, 27, 31, 45); ey = c(2, 2, 2.5, 3) pointDif(5,10, x,y, ex,ey) # 1.153846 * x + 4.230769 1.153846 * (x - 5 ) + 10 # 1.305556 * x + 3.472222 1.305556 * (x - 5 ) + 10 # I get the figure below on the right: # If I wanted to express the values in fractional: pointDif2(5,10, x,y, ex,ey) # 15/13 55/13 15/13 5 10 47/36 125/36 47/36 5 10 # I deduce: 15/13*x+55/13 15/13*(x-5)+10 47/36*x+125/36 47/36*(x-5)+10 # If I want to plot the points with their precision without approximating them with a # straight line, I use the following command, getting the figure above on the left: pointDif0(x,y, ex,ey) # If before these commands I put, for example, colRet="brown", the rectangles would # be drawn in brown. # If the precisions are all the same, if (for example) the points are N and ex are # all 2, I can put ex = rep(2,N). Other examples of use