# how to plot a straight line of the form y=w1*x1+w2*x2 in matlab

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shruti on 7 Jan 2015
Commented: Amit on 7 Jan 2015
y=w1*x1+w2*x2
x1=[2 10 6 6 1 1 -1 -1]
x2[2 6 6 10 1 -1 -1 1]
w1=0.0839
w2=0.0839
how to plot the line separating these points
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David Young on 7 Jan 2015
What is the independent variable?
shruti on 7 Jan 2015
no independent variables

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### Answers (3)

John D'Errico on 7 Jan 2015
Edited: John D'Errico on 7 Jan 2015
You appear to have TWO independent variables, x1 and x2, and a dependent variable, y. As such, this would be a plane in 3 dimensions, thus (x1,x2,y), not a line.
Possibly you want to plot a line in the plane (x1,x2), given the picture, and the fact that you have supplied the coefficients w1 and w2. That line goes through the origin as you have written it though, with a slope of -1.
As far as "separating" some points, it is not obvious what you are trying to separate. The words "discriminating hyperplane" do suggest something, but you have supplied only a fractional part of what that would involve.
I think you need to...
- Talk to your teacher and try to understand what you seem to be confused about.
- Reread your lecture notes. If you don't have any, why not? Take better notes.
- Read your textbook. AGAIN.
- Finally, it is often the case that two students can help each other. Work groups are a great way to resolve problems like this, where each of you helps the other to understand the problems. Do your own work of course, but some discussion time about HOW to do it can be invaluable.
When someone cannot explain their problem clearly, it is almost always a sign that they don't understand what they are asking about. So go back to your notes.
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Amit on 7 Jan 2015
Nice to-do-list!
John D'Errico on 7 Jan 2015
:)
Too often when someone posts a very fuzzy, very confused question like this, it just means they have no idea what it is they are doing. So for me the rational solution is for them to sit down and figure out enough about their problem that they do understand it. Of course then the answer often falls out as literally trivial.

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Titus Edelhofer on 7 Jan 2015
Hi,
what about
plot(y)
Titus
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Image Analyst on 7 Jan 2015
This works for me:
x1 = [2 10 6 6 1 1 -1 -1]
x2 = [2 6 6 10 1 -1 -1 1]
w1 = 0.0839
w2 = 0.0839
y = w1 * x1 + w2 * x2
plot(y, 'bo-');
ylabel('y', 'FontSize', 25);
xlabel('The Index of y', 'FontSize', 25);
Star Strider on 7 Jan 2015
I think OP wants to do something like gscatter as depicted in the documentation for classify.

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Amit on 7 Jan 2015
Y = w1*x1 + w2*x2;
I am not sure what is you independent variable (For example, you plot y as a function of x but here you have x1 and x2). I am assuming that you want to plot a 3D plot showing the correlation between y versus x1 and x2.
plot3(x1,x2,Y);
or
scatter3(x1,x2,Y);
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David Young on 7 Jan 2015
If you look at the comments, you'll see that I already asked about the independent variable, and shruti said that there isn't one, which doesn't really make sense.
Amit on 7 Jan 2015
I know :P. Which is why I took the liberty of interpreting the best I could !

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