10.12. A histogram¶
It is often useful to take the data from the previous tables and store
them for later access, rather than just print them. What we need is a
way to store 10 integers. We could create 10 integer variables with
names like howManyOnes, howManyTwos, etc. But that would require
a lot of typing, and it would be a real pain later if we decided to
change the range of values.
A better solution is to use a vector with size 10. That way we can create all ten storage locations at once and we can access them using indices, rather than ten different names. Here’s how:
int numValues = 100000;
int upperBound = 10;
vector<int> vector = randomVector (numValues, upperBound);
vector<int> histogram (upperBound);
for (int i = 0; i < upperBound; i++) {
int count = howMany (vector, i);
histogram[i] = count;
}
I called the vector histogram because that’s a statistical term for a vector of numbers that counts the number of appearances of a range of values.
The tricky thing here is that I am using the loop variable in two
different ways. First, it is an argument to howMany, specifying
which value I am interested in. Second, it is an index into the
histogram, specifying which location I should store the result in.
- Vectors require more typing than using individual variables to store data.
- Incorrect! Vectors require less typing than using individual varaibles to store data.
- Vectors create multiple storage locations at once under the same name.
- Correct!
- Once you store something in a vector, you cannot change its value.
- Incorrect! The values of vector elements can always be changed.
- Each storage location of a vector is accessed by indexing.
- Correct!
Q-1: Which of the following statements are true about using vectors to store data?
Before you keep reading...
Runestone Academy can only continue if we get support from individuals like you. As a student you are well aware of the high cost of textbooks. Our mission is to provide great books to you for free, but we ask that you consider a $10 donation, more if you can or less if $10 is a burden.