how to draw the line of known slope and intercept

Hello, I have a line which is in the form ax+by+c=0, with a,b and c known. In addition, I have a specific (x,y) point known, and the line should pass through it. How can I draw this line in matlab?

Answer 1

[Walter Roberson]

If a*x + b*y + c = 0 then b*y = - c - a*x and then provided b is non-zero, y = -c/b - a/b * x

Then if the line is to pass through a specific (x,y) the only thing you have to worry about is ensuring that the range of x you plot includes the specific x .

For example,

x = 15:41;
y = -19/11 - (-3/2)/11 * x;
plot(x,y)

Answer 2

[Daniel Shub]

I like refline

doc refline

Answer 3

[Matt Fig]

You could also do it using MATLAB's polynomial functions...

% Data
a = -2;
b = 3;
c = 8;
x = 3;
y = -2/3;

% Now the plotting.
pp = [-a,-c]/b; % Polynomial as MATLAB likes it.
X = linspace(x-1,x+1);  % Where to plot the line...
pv = polyval(pp,X);  % Evaluate the polynomial.
plot(X,pv,'-b',x,y,'*r')

Answer 4

[noor]

Hello, I'd like to know the slope for image 2D array. Need I draw line of known the slope? Thanks a lot

[Walter Roberson]

slope of a 2D array is a completely different concept. Please open a new Question for this, if you have not already done so.

Answer 5

[Amr Aboughazala]

for a line ax + by - c

you can draw the line using the coefficients as follows,

y = -(a*x+c) / b