Uploading matrix transformations example

Author: algorithmica-repository

6.linear-algebra/matrix-tranformations.R

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+draw.segment <- function(p1,p2,color,width=3) {
+  segments(p1[1],p1[2],p2[1],p2[2], col=color, lwd=width)
+}
+
+plot(NULL,xlim=c(-3,3),ylim=c(-3,3),ylab="y",xlab="x")
+
+# draw a segment (initially at 45 degrees)
+p.init <- matrix(c(0,0),2,1)
+p.end  <- matrix(c(2,2),2,1)
+draw.segment(p.init, p.end, "red")
+
+# rotation example
+theta <- pi/4  # rotate more 45º degrees 
+rotate.matrix <- matrix(c( cos(theta),sin(theta),
+                           -sin(theta),cos(theta)),2,2)
+
+p1.init <- rotate.matrix %*% p.init
+p1.end  <- rotate.matrix %*% p.end
+draw.segment(p1.init, p1.end, "blue")
+
+# scaling example
+scalingx <- 0.5  # scale both axis by 50%
+scalingy <- 0.5
+scale.matrix <- matrix(c(scalingx,    0,
+                         0,     scalingy),2,2)
+
+p2.init <- scale.matrix %*% p.init
+p2.end  <- scale.matrix %*% p.end
+draw.segment(p2.init, p2.end, "green")
+
+plot(NULL,xlim=c(-3,3),ylim=c(-3,3),ylab="y",xlab="x")