Multiple Linear Regression using "REGRESS"

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Priya
Priya 2013-10-5
评论： dpb 2013-10-15
Hello
I am using regress function for multiple linear regression analysis. Once I obtain the values of coefficients, I substitute in the equtation to get the new / predicted values of y.
Then I make the scatterplot of y_original and y_predicted. How can I show the regression line for equation y = ax1 + bx2 + cx3 + d on this scatter plot ? What code should I write for this problem ?
Secondly, How can I find the random error for this multiple linear regression relationship ?
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Priya
Priya 2013-10-13
Thanks , this means I cannot plot a multidimensional plot, which can show me the relationship of all three variables (x1,x2,x3) with y ????
Secondly, every regression equation has some random error associated with it. How can we find that random error and what can we conclude out of it ? How shall we interpret that random error ?
Thanks

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回答（2 个）

dpb
dpb 2013-10-5
s=sprintf('y = %.2f*ax1 + %.2f*x2 + %.2f*x3 + %.2f', b); text(x,y,s)
b is the coefficient matrix from regress; x, y are the coordinates of location where you wish to write the equation in the units of the x- and y-axes used for scatter
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Priya
Priya 2013-10-13
Thanks , this means I cannot plot a multidimensional plot, which can show me the relationship of all three variables (x1,x2,x3) with y ????
Secondly, every regression equation has some random error associated with it. How can we find that random error and what can we conclude out of it ? How shall we interpret that random error ?
Thanks
Priya
Priya 2013-10-15
@ Image Analyst :
Thanks. Now after applying regress, I get the coefficients a,b,c,d for the following equation:
y_predicted = a.x1 + b.x2 +c.x3 + d
When I substitute these coefficients a,b,c,d along with x1 dataset, x2 dataset, x3 dataset respectively into the equation,I will get the y_predicted dataset. For making a scatter plot between y_original dataset and y_predicted dataset, I use use the following command:
plot(y_predicted,y_original,'o')
Question is:
How can I show the line representing the above equation ( y_predicted = a.x1 + b.x2 +c.x3 + d ) on this scatter plot ?

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Priya
Priya 2013-10-13
Thanks , this means I cannot plot a multidimensional plot, which can show me the relationship of all three variables (x1,x2,x3) with y ????
Secondly, every regression equation has some random error associated with it. How can we find that random error and what can we conclude out of it ? How shall we interpret that random error ?
Thanks
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Priya
Priya 2013-10-15
No, in this case I have only two variables : y_predicted which is obtained by substituting the values in the above regression equation and y_original (input y dataset).
I can plot the scatter plot, but don't know how to show the line on the plot.
Is it possible to show the line represented b this equation on the scatter plot.
dpb
dpb 2013-10-15
编辑：dpb 2013-10-15
Oh, misinterpreted the question or the intended use of "line" -- that there's no line on the plot by your above command is because that's what you told it to do...
plot(y_predicted,y_original,'o')
says use the 'o' marker; you didn't specify a line style so Matlab obeyed and didn't, either. Use
plot(y_predicted,y_original,'o-')
or alternate linestyle of choice.
doc plot % documents above behavior and marker/linestyle choices

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