Prog-PC1: Attaway Chapter 1

Transcription

1 Prog-PC1: Attaway Chapter 1 Name: Student nr: 6. Think about what the results would be for the following expressions and then type them in to verify your answers. >> 25 / 4 * 4 25 >> ^ 2 1 >> 4 \ >> 3 ^ 2 >> (5-2) * The function sin calculates and returns the sine of an angle in radians. Use help elfun to find the name of the function that returns the sine of an angle in degrees. Verify that calling this function and passing 0 degrees to it results in 1. >> sind(0) Wind often makes the air feel even colder than it is. The wind chill factor (WCF) measures how cold it feels with a given air temperature T (in degrees Fahrenheit) and wind speed (V, in miles per hour). One formula for the WCF is: WCF = T 35.7 (V 0.16 ) T (V 0.16 ) Create variables for the temperature T and wind speed V, and then using this formula calculate the WCF. Example: >> t = 20; >> v = 11; >> wcf = *t *v^ *t*v^0.16 wcf = Use intmin and intmax to determine the range of values that can be stored in the types uint32 and uint64.

2 >> intmin('uint32') 0 >> intmax('uint32') >> intmin('uint64') 0 >> intmax('uint64') Generate (using rand and randi) a random real number in the range from 0 to 1 rand real number in the range from 0 to 20 rand * 20 real number in the range from 20 to 50 rand*(50-20)+20 integer in the range from 0 to 10 (including boundaries) randi([0,10]) integer in the range from 0 to 11 (including boundaries) randi([0,11]) integer in the range from 50 to 100 (including boundaries) randi([50,100]) 23. Using the colon operator (:), create the following row vectors: >> 3: >> 1:.5: >> 5:-1: Using the linspace function, create the following row vectors: >> linspace(4,8,3) >> linspace(-3,-15,5) >> linspace(,5,3) 7 5

3 2. Create a vector variable vec; it can have any length. Then, write assignment statements that would store the first half of the vector in one variable and the second half in another. Make sure that your assignment statements are general, and work whether vec has an even or odd number of elements. (Hint: Use a rounding function such as fix.) >> vec = 1:; >> fhalf = vec(1:fix(length(vec)/2)) fhalf = >> shalf = vec(fix(length(vec)/2)+1:end) shalf = Find an efficient way (using the : operator) to generate the following matrix:: mat = Then, give expressions that will, for the matrix mat, refer to the element in the first row, third column refer to the entire second row refer to the first two columns >> mat = [7:10; 12: -2: 6] mat = >> mat(1,3) >> mat(2,:) >> mat(:,1:2) Generate a 3 x 5 matrix of random integers (hint: use randi), each in the range from 5 to 5 (including limits). Determine the sign of each element. >> mat = randi([-5,5], 3,5) mat = >> sign(mat)

4 41. Create a three-dimensional matrix and get its size. >> mat3d = ones(3,5,2) mat3d(:,:,1) = mat3d(:,:,2) = >> size(mat3d) Attaway Chapter On average, people in a region spend 8% to 10% of their income on food. Write a script that will prompt the user for annual income. It will then print the range that would typically be spent on food annually. Also, print a monthly range. Hint: use fprintf to format the output. % Calculates and prints the likely amount spent on food % based on annual income income = input('enter your annual income: '); fprintf('you are likely to spend between Eur %.2f\n',.08*income) fprintf('and Eur %.2f annually on food.\n\n',.1*income) % print the monthly range fprintf('this equals Eur %.2f to %.2f monthly.\n',.08*income/12,.1*income/12) 16. Plot exp(x) for values of x ranging from 2 to 2 in steps of 0.1. Place an appropriate title on the plot, and label the axes. % Plot exp(x) x = -2:0.1:2; y = exp(x); plot(x,y,'*') title('exp(x)') xlabel('x') ylabel('exp(x)') 17. Create a vector x with values ranging from 1 to 100 in steps of 5. Create a vector y, which is the square root of each value in x. Plot these points. Next, use the bar function instead of plot to get a bar chart instead.

5 clf x = 1:5:100; y = sqrt(x); plot(x,y,'*') title('sqrt(x)') figure(2) bar(x,y) title('sqrt(x)') 27. If a certain amount of money (called the principal P) is invested in a bank account, earning an interest rate i compounded annually, the total amount of money T n that will be in the account after n years is given by: T n = P (1 + i) n Write a function account() that will receive input arguments for P, i, and n, and will return the total amount of money T n. function totmoney = account(p,i,n) % Calculates the amount of money in an account % after n years at interest rate i with a % principal p invested % Format of call: account(p,i,n) % Returns total of money after n years totmoney = p * (1+i)^n; end 32. The cost of manufacturing n units (where n is an integer) of a particular product at a factory is given by the equation C(n) = 5n 2 44n + 11 Write a MATLAB script mfgcost that will prompt the user for the number of units n call a function costn that will calculate and return the cost of manufacturing n units print the result (the format must be exactly as shown next) Note: you have to write one script named mfgcost and one function costn (so TWO files)! mfgcost.m % Prompts the user for the number of units, calls a function to calculate % the cost for producing that many units, and prints this result n = input('enter the number of units: '); costpern = costn(n); fprintf('the cost for %d units will be Eur %.2f\n',n,costPerN) costn.m function out = costn(n) % Calculates the cost of manufacturing n units of a product % Format of call: costn(n) % Returns cost as 5*n^2-44*n+11 out = 5*n^2-44*n + 11; end

6 37. If the lengths of two sides of a triangle and the angle between them are known, the length of the third side can be calculated. Given the lengths of two sides (b and c) of a triangle, and the angle between them α in degrees, the third side a is calculated as follows: a 2 = b 2 + c 2 2 b c cos(α) Write a MATLAB script thirdside that will prompt the user and read in values for b, c, and α (in degrees), and then calculate and print the value of a with three decimal places. (Note: To convert an angle from degrees to radians, multiply the angle by π /180 ). The format of the output from the script should look exactly like this: thirdside % Calculates the third side of a triangle, given % the lengths of two sides and the angle between them b = input('enter the first side: '); c = input('enter the second side: '); alpha = input('enter the angle between them: '); alpha = alpha * pi / 180; a = sqrt(b^2 + c^2-2*b*c*cos(alpha)); fprintf('\nthe third side is %.3f\n', a) Hand in: Spot at least 5 errors in the following MATLAB script. The script prompts the user for temperature in degrees Celsius, and then F for Fahrenheit or K for Kelvin. The conversions are: F = C K = C Correct script % Converts a temperature from C to F or K cel = input('enter the temp in degrees C: '); fork = input('do you want F or K? ', 's'); if fork == 'F' fork == 'f' fprintf('the temp in degrees F is %.1f\n', /5*cel+32) else fprintf('the temp in degrees K is %.1f\n', cel ) end