topic Re: Plotting a Model set to 0 in Graphics Programming

Plotting a Model set to 0

Msjustice — Sat, 20 Dec 2014 19:19:36 GMT

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

Re: Plotting a Model set to 0

Reeza — Sat, 20 Dec 2014 19:30:44 GMT

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.

Re: Plotting a Model set to 0

Msjustice — Sat, 20 Dec 2014 19:57:09 GMT

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;

Re: Plotting a Model set to 0

Reeza — Sun, 21 Dec 2014 00:33:57 GMT

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

What are you expecting from a graph?

Re: Plotting a Model set to 0

djrisks — Sun, 21 Dec 2014 00:49:14 GMT

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

Re: Plotting a Model set to 0

Msjustice — Sun, 21 Dec 2014 02:42:05 GMT

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

Re: Plotting a Model set to 0

djrisks — Mon, 22 Dec 2014 17:16:28 GMT

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;