Often, certain data entries in a data set can be missing, corrupted, or invalid.

Question

Often, certain data entries in a data set can be missing, corrupted, or invalid. Computers often assign such entries with value of NaN (which stands for not-a-number). In MATLAB, the NaN functions similarly to numbers. For example, you could create a MATLAB array (2:5 NaN 7 8]. To see an important attribute of NaN that is different than a number, type NaN == NaN into the command window and observe the result. The below steps require you to use MATLAB features that can be helpful when using data sets. Follow the steps below: Create a 2D data array using the lines below (write them exactly as written below). rng(2); % line 1 A = randi(10,1000,1000); % line 2 A(randi(1e6,20,1)) = NaN; % line 3 Describe in words (in the command window) what line 3 in part a does. Clearly present the indices of the columns of A which contain a NaN. Replace any element of A that is NaN with a 0. Certain elements of A have the following characteristics: an even row number, an odd column number, and a value that is less than or equal to 5. Replace every element which has every listed attribute with a value of -41. Clearly report the sum of the values in A (1 number) in the command window.

Explanation / Answer

a)

Creation of a 2D array using the following code:

>> rng(2);%line 1
A=randi(10,1000,1000); %line2

>> A(randi(1e6,20,1))=NaN; %line3

When executed, the array A will create an 2D array with 1000 rows and 1000 column.

b)

Line 2 A=randi(10,1000,1000); of the code will an 2D array with 1000 rows and 1000 column.

All the values of the array will be less than 10.

Line 3 A(randi(1e6,20,1))=NaN; of the code with will generate a number for all the vales of the array where the value is NaN.

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