# 2.1: struct Examples and Exercises

- Page ID
- 85177

By Carey A. Smith

##### Structure for simulation of the effect of an earthquake

% The magnitude 6.7 Northridge, California, earthquake of 17 January 1994

% https://pubs.er.usgs.gov/publication/70017610

Earthquake.name = 'Northridge';

Earthquake.year = 1994;

Earthquake.mag = 6.7;

Earthquake.length = 15; % km

Earthquake.vertical = 70; % cm max vertical movement

% https://en.Wikipedia.org/wiki/1994_N...dge_earthquake

Earthquake.duration = 20; % seconds

Earthquake.accel_g =1.82; % g

Earthquake.accel_ms2=Earthquake.accel_g*9.81; % m/s^2

% Simulation parameter

Earthquake.scale = 1.4; % Scale factor for simulations

###### Solution

Add example text here.

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- Create a struct for a team of 5 basketball players. They may be men or women, real or fictional. For each member of the team create struct called "player".
- Create the following fields in the "player" structure for each player.:
- Name (a string)
- Position (Choose one of these ‘Center’, ‘Power Forward’, ‘Small Forward’, ‘Shooting Guard’, ‘Point Guard’)
- Height in inches (not feet) Example: 75
- Shirt number

- Fill in you teams structure array with a separate sub-structure for each of the 5 starting players.
- Example. Suppose you had already filled out the structures for the 1st 4 players. Then the 5th substructure could be defined as follows:

player(5).Name = 'Kareem';

player(5).Position= 'Center';

player(5).Height = 84;

player(5).Shirt = 33;

- Create a “for loop” that displays each player’s information on one line. Each field should be separated by a tab “\t” or by 4 spaces. Use \n at the end of the format string to put a new line after each player's info.
Example:

fprintf(' Name Position Height Shirt\n') % \n creates a "new line"

for n=1:5

fprintf('%13s \t%14s \t%i \t %i\n', ... % \t inserts a tab

player(n).Name, player(n).Position, ...

player(n).Height, player(n).Shirt)

end

**Answer**-
Create your own struct.

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This example creates a triangle struct and uses it to draw 2 right triangles on one figure.

The first routine sets the parameters of each triangle.

The second file is a function that draws a triangle using the parameters in the struct. Only one argument, the struct, is passed to the function. Thus, a struct can group related variables and simplify function calls.

%% Triangle structure demo

clear all, format compact, format shortg; close all; fclose all; clc;

% 1st triangle

Tri1.pos = [-9,-1];

Tri1.width = 18;

Tri1.height= 28;

Tri1.color = 'b';

%% Double-click on a structure in the Workspace to see the details

figure;

draw_triangle(Tri1);

axis equal

%% 2nd triangle

Tri2.pos = [0,4];

Tri2.width = 8;

Tri2.height= 16;

Tri2.color = 'r';

hold on;

draw_triangle(Tri2);

function [] = draw_triangle(Tri)

% Draw a right triangle

x = zeros(1,4); % Need 4 points (1st & last are the same)

y = x;

% 1st point

x(1) = Tri.pos(1);

y(1) = Tri.pos(2);

% 2nd point: to the right, with the same y as point 1

x(2) = x(1) + Tri.width;

y(2) = y(1);

% 3rd point: up, with the same x as point 1

x(3) = x(1);

y(3) = y(1) + Tri.height;

% Last point = 1st point

x(4) = x(1);

y(4) = y(1);

% Debug

x = x

y = y

plot(x,y,Tri.color,'Linewidth',3);

###### Solution

This is the resulting plot:

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The logic and code for this exercise is similar to the

1. [5 pts] Create 3 rectangle structures that specify the position, size, and color of 3 rectangles with these characteristics:

% Rectangle 1

rect1.pos= [30,20]; % x and y coordinates of the lower left corner

rect1.width = 500;

rect1.height= 400;

rect1.color = 'b';

% Rectangle 2

rect2.pos= [350,300]; % x and y coordinates of the lower left corner

rect2.width = 220;

rect2.height= 250;

rect2.color = 'r';

% Rectangle 3

rect3.pos= [300,250]; % x and y coordinates of the lower left corner

rect3.width = 150;

rect3.height= 400;

rect3.color = 'c';

2. [7 pts] Write a draw_rectangle(rect) function whose uses a rect structure to plot 1 rectangle. Since variables in a function are local, you can use "rect" for the structure name inside the function. You don't need to use rect1, rect2, rect3.

3. [3 pts] Open a figure, use ”hold on;” and plot these 3 rectangles by calling your rectangle plotting function with each of the 3 rectangle structures.

- Helps:
- Like the draw_triangle function, the draw rectangle function needs to create an x vector & a y vector with the coordinates of the corners. In order to get back to the starting point & close the rectangle, you will need to have 5 pairs of (x,y) coordinates, with the last coordinate being the same as the first coordinate.
- The 1st corner is like home plate. It is in the lower-left corner.
- The 2nd corner is like 1st base. It’s x-coordinate is the 1st corner’s x-coordinate + the width of the rectangle. It’s y-coordinate is the same as the 1st corner’s .
- The 3rd corner is like 2nd base. It’s x-coordinate is the same as the 2nd corner. It’s y-coordinate is 2nd corner’s y-coordinate + the height of the rectangle.Figure out the coordinates of 3rd base. The last line goes from 3rd base to home plate.
- To plot each of the 4 lines, the 1st argument of plot() is a vector of the X coordinates.The 2nd argument of plot() is a vector of the Y coordinates.

**Answer**-
The resulting plot should look like this:

Add texts here. Do not delete this text first.

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