New Contributor
Posts: 3

# Plotting a Model set to 0

I have to plot the line 0 = alpha +beta(x)

I've only used the proc gplot a few time and am not sure if I can set a plot an equation set to zero. How can I go about doing so? Thank you

Super User
Posts: 21,578

## Re: Plotting a Model set to 0

Don't know if that helps...

You usually have y=beta(x) + e but if you want to force that to 0 you can subtract y:

0=beta(x) + e - y

And then e-y becomes your alpha.

Also,,

0=alpha+beta(x) => -alpha=beta(x)

so that's another way, but it depends on what you want for a plot I suppose.

New Contributor
Posts: 3

## Re: Plotting a Model set to 0

thank you, that makes sense. How would I plot that using sas?

would it be

proc gplot data = test;

y = 0;

plot y*x; run;

Super User
Posts: 21,578

## Re: Plotting a Model set to 0

What does your data look like, can you post sample data?

What are you expecting from a graph?

New Contributor
Posts: 3

## Re: Plotting a Model set to 0

Here is a small sample. It's the HIV status (1=present) and the person's age in months. I have to see if month is a predictor for HIV status.

I'm asked to plot the line 0 = alpha + month(x) + month*month(w) and compare it to the scatterplot of month by month*month. I was able to do that scatterplot but I don't know what the code would be to plot the line.

Month HIV

15        1

157      0

36        0

234      1

130      0

81        0

11        1

Super Contributor
Posts: 257

## Re: Plotting a Model set to 0

If you have SAS 9.2 or more you could use the REFLINE statement within PROC SGPLOT, to obtain a horizontal line.

Super Contributor
Posts: 257

## Re: Plotting a Model set to 0

Does this help?

data dataset;
input month hiv;
cards;
15  1
157 0
36  0
234 1
130 0
81  0
11  1
;
run;

proc sgplot data = dataset;
scatter x = month y = hiv;
refline 0 / axis = y;
run;

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