EGR 102 Introduction to Engineering Modeling. Lab 10A Nested Programming II Iterative Nesting

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1 EGR 102 Introduction to Engineering Modeling Lab 10A Nested Programming II Iterative Nesting 1

2 Overview 1. Nested loops 2. Nested loop: Creating Arrays 3. Nested Loops: 2 Variable functions 4. Nested Loops and 3D Plotting 2

3 Types of Nested Programming There are several types of nested programming that will be covered in this unit. Nested Functions and Sub-Functions Nesting with if Statements Nesting with Loops Lab 10A is going to focus on nesting with loops. 3

4 Nested Loops Just like nesting if statements inside of loops, loops can also be nested inside one another. The case that this lesson will focus on is a for loop nested in a for loop Other configurations are possible, but this is the most straight forward in terms of explaining, understanding, and what you will be expected to be able to code. 4

5 Nested Loops Nesting loops creates what are commonly referred to as the inner and outer loop. The inner is the nested loop. The outer is the main loop. For every one iteration of the outer loop, the inner loop goes through all of its iterations. 5

complete before the outer can move on to the next index Like the hour hand

6 Nested Loops time = [0,0] hour = 0 min = 0 for i = 1:12 hour = i-1; for j = 1:60 min = j-1; time = [ hour, min] end min=0; end The inner loop has to fully complete before the outer can move on to the next index Like the hour hand (outer loop) and minute hand (inner loop) of a clock; 60 minutes pass for every 1 hour 6

7 Nested loop: Creating Arrays There are a couple of common applications for nested loops. One is using the loops to create arrays. This is done with appropriate indexing for each loop. Each loop should have its own unique index. i, j, and k are commonly used ones. Depending on how the indices are set up, one loop is responsible for the rows while the other is responsible for the columns. Nested ifs can also be added for analysis. 7

8 Nested Loops - Format Each loop has its own index. Here the outer uses i and the inner uses j. Calculations inside the inner loop are repeated with both loops. The inner loop goes through all of its iterations for each single iteration of the outer. The order of the indices also determines the shape of the resultant array. Here, i is associated with the rows, and j is associated with the columns. The dimensions and order the loops run are more clearly seen with the results on the next slide. 8

9 Nested Loops - Results The order the iterations are executed is more clearly seen with the result. i being associated with rows and j with columns is reflected by the array in 2 ways. 1. There are 5 rows and 10 columns. 2. The addition goes horizontally along the rows. This means the inner loop goes through all of its iterations (columns) for one of the outer (row). 9

10 2-Variable Functions The other frequent application is modeling 2-variable functions with nested loops. It is a naturally conducive arrangements as: Each variable is assigned to one loop The loops, by going through all of their iterations, perform all possible combinations of the two variables The result is an array that has values of resulting from all possible combinations with the values of each variable being associated with either the rows or columns. 10

11 2-Variable Functions f(x,y) = 2x + 3y^3 X - Values Y -Values Imagine that the red values are your x vector & the blue values are your y vector. The green values are then your Z array where Y(i) and X(j) would be used to create Z(i,j). 11

12 Nested Loops 2 Variable functions One of the common applications for nested loops is calculations with two variables. The result is an array with the rows associated with one variable and the columns the other. The contents of the array represent every possible combination of the two variables. The example is for the following calculation: 12

13 Nested Loops 2 Variable functions Similar to the earlier, example, each loop has its own index. These indices are based on the number of values of the variables. The calculation should use both indices to establish rows, columns, and the variables should use their relevant index. Be sure to pay attention to which variable is used with rows and which with columns! 13

14 Nested Loops 2 Variable functions Y X In this example, the value of y changes with each row and x changes with each column. This is why it is important to keep track of them! The values represent every combination of x and y used in the original f(x,y) equation that was shown earlier. 14

15 Nested Loops and 3D Plotting Because the applications using nested loops often result in the creation or manipulation of arrays, 3D plotting is often used with them to aid in the visualization of the work. For a reminder on plotting with surface, mesh, or contour plots, review Lab 5B. 15

16 Overview 1. Nested loops 2. Nested loop: Creating Arrays 3. Nested Loops: 2 Variable functions 4. Nested Loops and 3D Plotting 16

Introduction to Programming in C Department of Computer Science and Engineering. Lecture No. #16 Loops: Matrix Using Nested for Loop

Introduction to Programming in C Department of Computer Science and Engineering Lecture No. #16 Loops: Matrix Using Nested for Loop In this section, we will use the, for loop to code of the matrix problem.