Linear Algebra

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Exercise C10

In Example TMP the first table lists the cost (per kilogram) to manufacture each of the three varieties of trail mix (bulk, standard, fancy). For example, it costs $3.69 to make one kilogram of the bult variety. Re-compute each of these three costs and notice that the computations are linear in character.

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Code

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# Matrix of (kg/batch) Trail Mix
trails <- matrix(c(7, 6, 2, 6, 4, 5, 2, 5, 8), nrow = 3, ncol = 3)
trails
##      [,1] [,2] [,3]
## [1,]    7    6    2
## [2,]    6    4    5
## [3,]    2    5    8

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# Find Batches (trails divided by 15)
trails_batch <- trails/15
trails_batch
##           [,1]      [,2]      [,3]
## [1,] 0.4666667 0.4000000 0.1333333
## [2,] 0.4000000 0.2666667 0.3333333
## [3,] 0.1333333 0.3333333 0.5333333

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# Cost of Trail Mix
trails_cost <- matrix(c(3.69, 3.86, 4.45), nrow = 3, ncol = 1)
trails_cost
##      [,1]
## [1,] 3.69
## [2,] 3.86
## [3,] 4.45

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# Solve to check for linearity
results <- solve(trails_batch, trails_cost)
results
##      [,1]
## [1,] 2.55
## [2,] 4.65
## [3,] 4.80

Conclusion

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Since the values do not change within the matrix and there’s no other computations being done, if these results were to be plotted then there would be straight lines.