Cats. Cats are often used in studies about locomotion and injury recovery. In one such study, a bundle of nerves in a cat’s legs were cut and then surgically repaired. This mimics the surgical...

Cats. Cats are often used in studies about locomotion and injury recovery. In one such study, a bundle of nerves in a cat’s legs were cut and then surgically repaired. This mimics the surgical correction of injury in people. The recovery process of these cats was then monitored. It was monitored quantitatively by walking a cat across a plank that has force plates, as well as by monitoring various markers inside the leg. These markers provided data for measures such as joint lengths and joint moments. A variety of data was collected from three different cats: Natasha, Riga, and Korina. Natasha (cat = 1) has 47 data entries, Riga (cat = 2) has 39 entries, and Korina (cat = 3) has 35 entries. The measurements taken are the number of steps for each trial, the length of the stance phase (in milliseconds), the hip height (in meters), and the velocity (in meters/second). The researchers observe these variables for different reasons. They want uniformity both within and between samples (to prevent confounding variables) for steps and velocity. The hip height helps monitor the recovery process. A detailed description can be found in Farrell et al. (2009). The data set, courtesy of Dr. Boris Prilutsky, School of Applied Physiology at, Georgia Tech, is given as the MATLAB structure file cats.mat. Form a data matrix X = [cat.nsteps cat.stancedur cat.hipheight cat.velocity cat.cat]; and find its mean and correlation matrix. Form matrix Z by standardizing the columns of X (use zscore). Plot the image of the standardized data matrix.