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Modifying arrays

From: Interactive Data Visualization with Processing

Video: Modifying arrays

In our last movie, we learned how to create arrays of data, that is, a collection of data points that are all of the same variable type such as ints, floats, but getting an entire collection you're can to refer to as a single thing. In this one, I want to show you how to work with arrays and perform a handful of different functions on them. I'm going to start by naming my file here, just as a comment in my own file, and then I'm going to create an array. It's going to be integer variables and I put the square brackets to indicate that it's an array.

Modifying arrays

In our last movie, we learned how to create arrays of data, that is, a collection of data points that are all of the same variable type such as ints, floats, but getting an entire collection you're can to refer to as a single thing. In this one, I want to show you how to work with arrays and perform a handful of different functions on them. I'm going to start by naming my file here, just as a comment in my own file, and then I'm going to create an array. It's going to be integer variables and I put the square brackets to indicate that it's an array.

Give it a name, I'll just simply call this one 'a', and then I'm going to put in curly brackets {7, 0, 4}, and those would be the three values that are going to be in my array. We can double-check that and you'll see that the 7, 0, and 4 appear at the bottom with their index numbers 0, 1, and 2, great. The next thing I want to do though is I want to copy this array. Now one way to do this, is to create an empty array, also of integer variables, I'll call it 'b' and then instead of entering values manually, I'm going to create a new one.

It's going to be integers and then the square brackets; I'll have to put the length of the array. This one is going to eventually be a copy of 'a', I want it to be the same length. What I can do is I can say 'a' because that's the name of the other array and .length, and that's a built-in things that says, find out how many items there are in the array 'a'. And so now I've created this one. Watch what happens if I print 'b' you'll see that I have zeros in it, because it's not filled in yet.

I'm going to comment this one out, so now all I have is zeros. On the other hand what I can do here is I can say arrayCopy. And what does this means is to take array 'a' and copy it into 'b', so you start with the source array and then you have the destination array. And when I do that, of course, if this is going to work, I'm going to have to go and 'a' is going to have to show again, but I don't need to print it.

Now that I've got that I can run this through. And you can see that at first the three values in 'b' are 0, 0, 0 because it was an empty array, and then they got replaced with the copies of the values from 'a'. Another command is to sort an array. You see that these values are out of order. They're 7, 0, 4, what I'm going to do is, I'm going to resort 'a', and I'm going to say as 'a', that's the array, is equal to sort of itself 'a'.

Make sure we get an equal sign in there and then when I click that, now nothing's going to show different because I haven't printed it. I'm just going to comment out the print commands. And now you can see what happens is if I do a print line 'a' and run it and now instead of being 7, 0, 4 now they're in order of 0, 4, 7. So we have sorted values now. Let's say on the other hand I want it to be a descending order, what I can do is I can reverse it.

And all I have to do for this one is all I am going to actually work with 'b' right now. Now 'b' still has these original three values in their unsorted order 7, 0, 4. I'm going to create a new array called bReverse, and this is pretty simple. And I got to type is in reverse (b), and when I do that, comment that out. Instead of 7, 0, 4 it says 4, 0, 7.

So it has taken the original and just switched it around in order. The next thing we are going to do, is we're going to add things in an array with the Append function. What you need to specify is the destination array. In this case, I'm going to add these items on to 'a' itself and then the function name is append. You give the source array which is 'a', and then I'm going to add an 8 to it. And now I'm going to copy this, bring it down, uncomment that, I will comment this one out.

Now when I run it, you see that 'a' is now 0, 4, 7, and one additional value 8. Now append adds an item to the end of the array. Let's say for instance, I want to add something to these middle of an array, I can use the Splice command. And in this case, I'll take array 'b' and splice it into itself. So first I say the source array is 'b' and then I give the value that I want to splice, it's going to be 10.

And this says where I want to put it? I want it to be at index number two in the array, and when I do that, it helps if I do print line. You can see we've gone from the 7, 0, 4 to 7, 0, 10, 4. Again, it's index number that it went in, so it would be the third item in the particular array. If I want to combine two arrays I have the option of concatenating them.

And the way that works is I'm going to create a new array in this particular case. An int array that I'll call 'c' and it'll be the concat of array 'a' and array 'b', that's all there is to it. You just specify the two that you're going to deal with. And it will do the print line for that. And now you can see this one's longer because array 'a' adds three items.

I'm going to make this a little taller. I have the 0.7 that I got sorted earlier than I added an add-on and then array 'b' I had spliced a 10 into but it hasn't been sorted. Anyhow, there's all of that. Processing actually has several other functions for dealing with arrays, such as shortening and taking subsets and you can explore those in the Processing reference, but for right now, I want you to see that there are ways of modifying arrays of sorting them, of expanding, rearranging them, they can be helpful in creating our own data visualizations and other works later.

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This video is part of

Image for Interactive Data Visualization with Processing
Interactive Data Visualization with Processing

72 video lessons · 12731 viewers

Barton Poulson
Author

 
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  1. 3m 16s
    1. Welcome
      58s
    2. What you should know
      1m 22s
    3. Using the exercise files
      56s
  2. 11m 51s
    1. Overview of data visualization
      11m 51s
  3. 11m 53s
    1. Installing Processing
      3m 38s
    2. Overview of Processing
      4m 5s
    3. Exploring libraries
      4m 10s
  4. 1h 1m
    1. Basic setup
      7m 31s
    2. Drawing points
      4m 37s
    3. Drawing lines
      5m 6s
    4. Drawing ellipses and circles
      5m 24s
    5. Drawing arcs
      6m 54s
    6. Drawing rectangles and squares
      4m 58s
    7. Drawing quadrangles
      3m 25s
    8. Drawing triangles
      2m 55s
    9. Drawing polygons
      3m 37s
    10. Drawing simple curves
      4m 54s
    11. Drawing complex curves
      6m 46s
    12. Drawing Bézier curves
      5m 38s
  5. 54m 3s
    1. Introduction to variables
      10m 44s
    2. Understanding variable scope
      6m 53s
    3. Modifying variables
      9m 8s
    4. Creating arrays
      9m 53s
    5. Modifying arrays
      6m 37s
    6. Creating strings
      7m 3s
    7. Modifying strings
      3m 45s
  6. 1h 2m
    1. Incorporating randomness
      7m 59s
    2. Using Perlin noise
      4m 24s
    3. Shuffling with Java
      3m 30s
    4. Specifying line attributes
      8m 2s
    5. Changing placement modes
      5m 45s
    6. Understanding color attributes and functions
      4m 16s
    7. Exploring color spaces
      7m 44s
    8. Using color palettes
      7m 5s
    9. Transforming the grid
      8m 38s
    10. Exploring the attribute matrix
      5m 33s
  7. 52m 7s
    1. Building code blocks
      5m 57s
    2. Writing a while loop
      3m 52s
    3. Using for loops
      5m 35s
    4. Creating conditionals
      14m 50s
    5. Working with easing
      10m 51s
    6. Creating spirals
      11m 2s
  8. 18m 55s
    1. Mouse tracking
      3m 54s
    2. Hovering and clicking
      11m 16s
    3. Understanding keyboard interaction
      3m 45s
  9. 27m 32s
    1. Specifying fonts
      6m 43s
    2. Using images
      5m 51s
    3. Playing a video loop
      6m 20s
    4. Exporting video
      3m 47s
    5. Adding sound
      4m 51s
  10. 20m 49s
    1. Creating functions
      11m 48s
    2. Creating classes and objects
      9m 1s
  11. 31m 10s
    1. Using embedded data
      5m 26s
    2. Working with appended text data
      6m 4s
    3. Working with appended tabular data
      10m 26s
    4. Reading XML data
      9m 14s
  12. 48m 17s
    1. Generating dot plots
      11m 11s
    2. Building scatter plots
      10m 0s
    3. Making line plots
      9m 55s
    4. Creating bar charts
      9m 12s
    5. Checking out examples of maps, hierarchies, and networks
      7m 59s
  13. 20m 57s
    1. Introducing some principles of 2D design
      13m 44s
    2. Understanding color theory
      7m 13s
  14. 24m 46s
    1. Interacting with zooming, rotating, and sliding
      6m 26s
    2. Implementing slicing
      6m 47s
    3. Using rollovers
      5m 58s
    4. Introducing the GUI libraries
      5m 35s
  15. 10m 35s
    1. Sharing via OpenProcessing and other sites
      3m 19s
    2. Saving as a desktop application
      2m 42s
    3. Saving as JavaScript
      1m 47s
    4. Saving as an Android application
      2m 47s
  16. 2m 38s
    1. Where to go from here
      2m 38s

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