MATLAB regression tree analysis

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I have five different images, size is 9000rows and 9000columns. I want to calculate the index using following rules . the rules are (1) if image1<= 4.6 and image2 in R, D then index = 734.5 + 437 image1

(2)if image1 > 4.6 and image2 = E then index = 3869.4 + 6 image1 + 8 image3 - 7 image4

(3)if image1 > 4.6 and image2 in R, P and image5 <= 0.73 then index = 3639.5 + 388image1 - 4439 image5

I want to make the index image. can any one please tell me how can I do this.

if image size is a problem(9000*9000), can you please tell how to do it for 100*100 image