Finding the equation of a line passing 2 points
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Hello, I have two points (x1,y1) and (x2,y2). Now I want to find the linear equation of a line passing through these 2 points. The equation must be like f(x)=a*x+b. Is there any function in matlab that accepts coordinates of two points an gives the related linear equation back? If not, I know that a=(y2-y1)/(x2-x1) but what is the short and easy way to find 'b'? Thanks in advance!
1 个评论
Ahmed
2021-12-27
You can select Polynomial of degree 1 from the cftool
this will give you something like this
Linear model Poly1:
f(x) = p1*x + p2
Coefficients:
p1 = xx
p2 = xx
where xx could be any number
采纳的回答
Image Analyst
2016-7-16
Try polyfit:
coefficients = polyfit([x1, x2], [y1, y2], 1);
a = coefficients (1);
b = coefficients (2);
5 个评论
Image Analyst
2022-11-27
@Jose then define it. Certainly you must know what points you fit the line through. So, what variable names did you use? Use those instead of x1, etc.
更多回答(3 个)
Star Strider
2016-7-16
A third (and probably the most efficient) option for this particular problem:
x = [1 2];
y = [5 4];
c = [[1; 1] x(:)]\y(:); % Calculate Parameter Vector
slope_m = c(2)
intercept_b = c(1)
slope_m =
-1
intercept_b =
6
This uses the mldivide,\ operator to do a least-squares fit of the points.
2 个评论
Alok Mishra
2022-9-15
编辑:Alok Mishra
2022-9-15
function [a b c eq] = makeEquationFrom2Points(x1,y1,x2,y2) syms x y; if x1==x2 && y1==y2 disp('Need 2 distinct points'); a=NaN; b=NaN; c=NaN; eq="null"; return; else if x1==x2 b=0; a=1; c=x1; else %for lines m not_equal to inf %y=mx+c %m is coeff(1) and coeff(2) is c coefficient=polyfit([x1 x2],[y1 y2],1); a=-coefficient(1); c=coefficient(2); b=1; end eq=a*x+b*y==c; end
on workspace do:
[a b c eq]=makeEquationFrom2Points(1,2,3,4)
Output: a =
-1.0000
b =
1
c =
1.0000
eq =
y - x == 1
3 个评论
Image Analyst
2023-1-29
@navid seif put the function in a loop over x1
for k = 1 : numel(x1)
if x1(k) == x2(k) && y1(k) == y2(k)
% etc.
end
end
Everything should have an index k, like a(k), b(k), etc., so that you store the results for every set of data.
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