I'm trying to make something that would give me the slope and y-intercept from 2 points. Sometimes it would give me the correct values, but other times it would give me something close to correct but wrong.

Anyone know any thing that I could have done wrong? (Also, I feel like I should say that I'm just now starting to learn python)

y2 = input('Y2: ')
y1 = input('Y1: ')
x2 = input('X2: ')
x1 = input('X1: ')

y2 = float(y2)
y1 = float(y1)
x2 = float(x2)
x1 = float(x1)

over = y2-y1
under = x2-x1

m = over/under

y = float(y2)
x = float(x2)
m = float(m)

ym = y-m
b = ym/x

print(f'Y = {m}x   {b}')

CodePudding user response：

it appears as though the mathematics for the intercept b is incorrect.

it would be logical to use the x1, y1 coordinate with the slope to generate b.

assume that you want to find x0, y0 where y0 = b. Then you would do a similar calculation (already having calculated m before as you correctly did).

So (y1-b) / x1 = m. and you can just rearrange this to get: b = y1 - m*x1.

So this works:

x1, y1 = 1, 1
x2, y2 = 2, 2

over = y2-y1
under = x2-x1

m = over/under

b = y1 - m*x1

print(f'Y = {m}x   {b}')

returns this:

Y = 1.0x   0.0