Table-6 Counting Multiple Things

< CS101

Now that we have table counting, the natural thing to want to do is count multiple things to compare them.

• Count multiple things in the loop
• Have multiple counters:
  count1 = 0; // boy counter
count2 = 0; // girl counter
• Series of if-statements inside the loop (our official form)
    x = x + 1; -- within if-statement, correct variable
    Note the if-statements are not nested (more complex)
• After the loop, print both counters
• Alternative: could use more mnemonic variable names, like countBoy and countGirl

Do more boy or girl names end with "y"? We want a program which by the end prints "girl count:nn" and "boy count:nn", counting whatever characteristic we are looking for. This is beginning to look like an actual, practical use of computers to sift through data.

One approach is to use two (or more) counters, one for each case we want to count. Here we'll have one boy counter (count1) and one girl counter (count2). Initialize both counters to 0 before the loop. Then in the loop, have two if statements, one for each case we want to count. Inside each if-statement, increment the appropriate counter. At the end of the loop, print the counters.

It's possible to write the above code in different ways, but we will use that simple pattern: one if-statement for each case we want to count, and the if-statements are all in the loop, one after the other (not one if inside another).

3 Couuters - ending in a, i o?

Code example with 3 counters, just showing the natural extension of the 2-counters code above.

Class Survey

As another example of a table, we have the class survey of data from the live class at Stanford with people's favorite movies and what have you. The questions for this survey were:

• Gender: "male" or "female"
• What is your favorite color?
• What is your favorite current TV show?
• What is your favorite current movie?
• What is your favorite sport to play?
• What is your favorite current book?
• What is your favorite canned soda to drink?
• Field names for the survey table: gender, color, tv, movie, sport, book, soda

The survey answers are automatically translated to a google spreadsheet which can be exported in csv table. This data is available in the file "survey-2015.csv". This also illustrates that .csv format's role as an interchange format between systems.

Some data cleanup to make the answers consistent: changed "coca-cola" to "coke", "Navy" to "blue", "Dr. pepper" spelled with a period. Print the raw rows to see what the data looks like

The convertToLowerCase() function of the table changes all the text the table contains to lower case. This simplifies our logic, so we don't have to worry if someone typed in "Blue" or "blue" .. in the table it will always be the lowercase "blue" form. Therefore our query code should always look for the lowercase "blue" form. I cleaned up the data a bit for consistency, changing "Dark Blue" to just "Blue" and the many spellings of "Coca-Cola" to just "Coke", and things like that.

Survey Code - Example Problems

These can all be written using our "loop containing series of if-statements" form.

1. Write code to just print the soda field of each row, so we can get a feel for what people typed in. Note the effect of the convertToLowerCase() operation. Look at "color" and "sport" fields too.

2. Count 2 soda favorites: coke vs. sprite

3. Variant on (2) above, look only at people who's favorite color is blue

4. Variant on (2), use || to lump together for counting "coke" with "diet coke"

5. (You Try It) Count sports: soccer and volleyball

6. (You Try It) Variant of (5), count only gender female rows, then change to count male

Table code solutions:

// 1. just print the soda field

for (row: table) {
  print(row.getField("soda"));
}

// 2. count coke, sprite

count1 = 0;
count2 = 0;
for (row: table) {

  if (row.getField("soda") == "coke") {
    count1 = count1 + 1;
  }

  if (row.getField("soda") == "sprite") {
    count2 = count2 + 1;
  }

}
print("coke count:", count1);
print("sprite count:", count2);

// 3. blue variant with &&
count1 = 0;
count2 = 0;
for (row: table) {

  if (row.getField("color") == "blue" &&
      row.getField("soda") == "coke") {
    count1 = count1 + 1;
  }

  if (row.getField("color") == "blue" &&
      row.getField("soda") == "sprite") {
    count2 = count2 + 1;
  }

}
print("coke count:", count1);
print("sprite count:", count2);

// 4. Use || to lump together multiple things

count1 = 0;
count2 = 0;
for (row: table) {

  if (row.getField("soda") == "coke" ||
      row.getField("soda") == "diet coke") {
    count1 = count1 + 1;
  }

  if (row.getField("soda") == "sprite") {
    count2 = count2 + 1;
  }

}
print("coke + diet coke:", count1);
print("sprite:", count2);

// 5. Count soccer vs. basketball

count1 = 0;
count2 = 0;
for (row: table) {

  if (row.getField("sport") == "soccer") {
    count1 = count1 + 1;
  }

  if (row.getField("sport") == "volleyball") {
    count2 = count2 + 1;
  }

}
print("soccer count:", count1);
print("volleyball count:", count2);

// 6. count sports, female only (

count1 = 0;
count2 = 0;
for (row: table) {

  if (row.getField("gender") == "female" &&
      row.getField("sport") == "soccer") {
    count1 = count1 + 1;
  }

  if (row.getField("gender") == "female" &&
      row.getField("sport") == "volleyball") {
    count2 = count2 + 1;
  }

}
print("soccer count:", count1);
print("volleyball count:", count2);

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