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Hi everyone,
OK, so plotting a graph, pretty straightforward:
X axis = concentration of the chemical (log transformed)
Y axis = percent mortality
BUT - how do I calculate the actual slope? Could you offer me code to do that? I am using SAS version 9.3 on a PC.
Example data points:
x = 4.20, y = 10
x = 4.27, y = 20
x = 4.29, y = 30
x = 4.58, y = 40
x = 4.73, y = 50
x = 4.82, y = 60
Thank you!
Peppy
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Use the INSET statement to display the slope after you've computed it: How to use PROC SGPLOT to display the slope and intercept of a regression line - The DO Loop
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m = (y2-y1)/(x2-x1) or assuming you have the pairs and want the slope from the previous point;
data want;
set have;
slope = (y - lag(y))/(x-lag(x));
run;
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data have;
input x y;
datalines;
4.20 10
4.27 20
4.29 30
4.58 40
4.73 50
4.82 60
;
ods output parameterEstimates=slope;
proc reg data=have;
model y=x;
run;
proc print data=slope;
run;
Slope dataset will have intercept and slope.
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I couldn't find an easy way to add the slope in to the graph automatically. GPLOT provides the entire regression equation but its at the bottom and not pretty.
data have;
input x y;
cards;
4.20 10
4.27 20
4.29 30
4.58 40
4.73 50
4.82 60
;
run;
ods output parameterEstimates=slope;
proc reg data=have;
model y=x;
run;
proc sql noprint;;
select Estimate into :slope from slope where variable='x';
quit;
proc sgplot data=have;
scatter x=x y=y;
reg x=x y=y/degree=1 curvelabel="Slope=&slope" curvelabelpos=end;
run;quit;
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Use the INSET statement to display the slope after you've computed it: How to use PROC SGPLOT to display the slope and intercept of a regression line - The DO Loop
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Thank you all so much! This is so helpful - this will really assist me. I appreciate your time!