@koyelghosh.I guess it is a variation of our last suggestion I am interested in. Is the indvidual linear regression coefficient for each of the four curves significantly different. I get these results from the proc reg, but do these curves differ?   Label Diet Intercept Slope 6.222 + 3.030 * Week A 6.22222 3.02976 6.214 + 3.205 * Week B 6.21389 3.20476 5.917 + 3.024 * Week C 5.91667 3.02381 5.842 + 3.343 * Week D 5.84167 3.34286     This is what I get from the curve for diet A, (I get similar information for the regression of diet B, ,C, and D) but no comparision between the four diets   Analysis of VarianceSource DF Sum ofSquares MeanSquare F Value Pr > FModelErrorCorrected Total 1 1927.68601 1927.68601 189.68 <.0001 70 711.39385 10.16277     71 2639.07986       Root MSER-SquareDependent MeanAdj R-SqCoeff Var  3.18791 0.7304 16.82639 0.7266 18.94589   Parameter EstimatesVariable Label DF ParameterEstimate StandardError t Value Pr > |t|Intercept1Week1 Intercept 6.22222 0.85673 7.26 <.0001 Week 3.02976 0.21999 13.77 <.0001 ... View more

@Rick_SAS Thank you for the suggestions. I am a little unsure whether using Proc mixed will give me the answers I need. I use proc mixed for many of my studies, however (and correct me if I am wong) I normally use proc mixed to compare means. So if I do as you suggest, wouldn´t that just give me a comparision of the weight means overall at the time points used?  What I want is to compare the weekly increase, that is the slope of the growth curves. The important thing is not whether the absolute weight of animals on diet A is different from animals on diet B on so on, but I want to know whether the overall weekly increase differs.    I have attached an example of the curves with the slopes I want to compare (I will propably end up log transforming the values due to increasing variation, so the curves are just to give you an idea )         ... View more

@koyelghosh Thanks. Will your analysis perform a comparison between the four diets you have or just construct four different curves? I would like to determine whether the curves for my four diets differ (with a p value)  ... View more

 I didn´t realise that the proc mixed could give me the answers. I will look into that, thanks. ... View more

Below is an example of data. I have 48 pigs on 4 different diets. The weight is measured every week. Included data from week 1 and 2, but I have data for week 1-6   I have fitted the following linear regression, and would like to compare the slopes.     Label Diet Intercept Slope 6.222 + 3.030 * Week A 6.22222 3.02976 6.214 + 3.205 * Week B 6.21389 3.20476 5.917 + 3.024 * Week C 5.91667 3.02381 5.842 + 3.343 * Week D 5.84167 3.34286           Gris_ID Diet Weight Week 1 B 10 1 2 B 13 1 3 B 9,5 1 4 C 11,5 1 5 C 8,5 1 6 C 11,5 1 7 A 12,5 1 8 A 9 1 9 A 10,5 1 10 D 12 1 11 D 11,5 1 12 D 9,5 1 13 A 13,5 1 14 A 10,5 1 15 A 7,5 1 16 B 12,5 1 17 B 9,5 1 18 B 10,5 1 19 D 14,5 1 20 D 8,5 1 21 D 9,5 1 22 B 11 1 23 B 12 1 24 B 9 1 25 C 13,5 1 26 C 9,5 1 27 C 9 1 28 A 9,5 1 29 A 10,5 1 30 A 12 1 31 C 8,5 1 32 C 12,5 1 33 C 11,5 1 34 D 13 1 35 D 10 1 36 D 9 1 37 C 8 1 38 C 12 1 39 C 10,5 1 40 B 9,5 1 41 B 10,5 1 42 B 12,5 1 43 D 13,5 1 44 D 9 1 45 D 10 1 46 A 12 1 47 A 9,5 1 48 A 11 1 1 B 12,5 2 2 B 15 2 3 B 11,5 2 4 C 14 2 5 C 10 2 6 C 13 2 7 A 14 2 8 A 10,5 2 9 A 12,5 2 10 D 12 2 11 D 11,5 2 12 D 11,5 2 13 A 15 2 14 A 11 2 15 A 8,5 2 16 B 15,5 2 17 B 11,5 2 18 B 11 2 19 D 16,5 2 20 D 9 2 21 D 12 2 22 B 12,5 2 23 B 13,5 2 24 B 10,5 2 25 C 15,5 2 26 C 11 2 27 C 10,5 2 28 A 12,5 2 29 A 12,5 2 30 A 14 2 31 C 9 2 32 C 11,5 2 33 C 12,5 2 34 D 14,5 2 35 D 11,5 2 36 D 11,5 2 37 C 8 2 38 C 12,5 2 39 C 11 2 40 B 11 2 41 B 12,5 2 42 B 12,5 2 43 D 13,5 2 44 D 11 2 45 D 11,5 2 46 A 12 2 47 A 11,5 2 48 A 13 2 ... View more