Linear Plateau code assistance needed

[Trwhite]

I have been instructed to use a linear plateau for the data below.  I am confused with the overall coding linear plateaus that I have found here and other sources online.  I hope if I see it used with some of my own data, I will be able to make better sense of the code and apply it to my remaining data sets.  Any help would be greatly appreciated.  Thank you.

The data is looking at relative crop yields after four levels of crop destruction were applied.

Data: 

X= Severity

Y= RelYield

X	Y
0	84.364
0	107.463
0	90.044
0	118.130
25	80.726
25	100.291
25	88.546
25	87.870
50	76.977
50	76.065
50	82.529
50	67.358
75	76.575
75	82.847
75	103.377
75	81.920
0	92.807
0	133.470
0	94.579
0	79.145
25	109.281
25	98.694
25	140.440
25	110.404
50	94.516
50	93.878
50	90.349
50	92.902
75	66.631
75	82.134
75	94.602
75	64.348
0	105.355
0	104.519
0	98.055
0	92.071
25	98.167
25	142.057
25	121.168
25	94.243
50	89.909
50	99.378
50	140.359
50	106.142
75	71.665
75	86.498
75	80.806
75	99.886

[Reeza]

What is your definition of a 'linear plateau'?

Assuming you mean where does the curve flatten, do you remember the first derivatives concepts from calculus?

Where the first derivate is close to zero is likely what you're trying to calculate?

From the data shown what would you expect as output? What would you like to get back if that was your input exactly?

---

@Trwhite wrote:

I have been instructed to use a linear plateau for the data below.  I am confused with the overall coding linear plateaus that I have found here and other sources online.  I hope if I see it used with some of my own data, I will be able to make better sense of the code and apply it to my remaining data sets.  Any help would be greatly appreciated.  Thank you.

The data is looking at relative crop yields after four levels of crop destruction were applied.

Data: 

X= Severity

Y= RelYield

X	Y
0	84.364
0	107.463
0	90.044
0	118.130
25	80.726
25	100.291
25	88.546
25	87.870
50	76.977
50	76.065
50	82.529
50	67.358
75	76.575
75	82.847
75	103.377
75	81.920
0	92.807
0	133.470
0	94.579
0	79.145
25	109.281
25	98.694
25	140.440
25	110.404
50	94.516
50	93.878
50	90.349
50	92.902
75	66.631
75	82.134
75	94.602
75	64.348
0	105.355
0	104.519
0	98.055
0	92.071
25	98.167
25	142.057
25	121.168
25	94.243
50	89.909
50	99.378
50	140.359
50	106.142
75	71.665
75	86.498
75	80.806
75	99.886

---

[Trwhite]

Yes, I am hoping to see where the curve flattens on a graph as well as numerically.  Thank you for the provided link, it served as a nice review.  I believe the yields for severity levels 50 and 75% will display where the line flattens out from the data provided.

[Rick_SAS]

A "linear plateau" usually means that the explanatory variable is measured on a continuous scale ... or at least at more than four points. When the X variable is measured at many locations, you can use a "segmented regression" to estimate the point at which the data flattens out.  An example is shown in this article on segmented regression in SAS.

Personally, I don't think these data indicate a plateau. Graphing the data does not indicate a plateau:

proc sgplot data=Have;
   vbox y / category=x connect=mean;
run;