Hi, welcome to this new
video in our fifth week. So we're going to continue
with the idea of how to write and read
different file formats that we could use for, let's say, data visualization or for writing data that
could be used for others. In this case we're
going to be writing a table using CSV
file structure. So a CSV file stands for
a comma separated values. It's a file that understands
using delimiter, which in this case is
going to be the comma that we are actually in fact
trying to construct a table, that has columns and
rows, potentially, and this is an optional part
of it might have a header, So as you can see
here on the right, we have a table
that has a header specifying we have the X
coordinate, the Y coordinate, the Z coordinate, and then we have values that are
for each one of those. The CSV file, as we
can see on the bottom, really is very much
like a text file, but we're using those
commas with an intention, and we're going to see when
we open a file like this, something like Google
Sheets or Excel, that this file is going
to be interpreted correctly as a table. So let's see how we
can actually do that. We're going to use
the same class, the createWriter("Data.csv"),
and we're going to print lines
in the same way. But in this case we're
going to be combining variables and using the comma in between them to really construct something that could be
understood as a CSV file. So we're definitely
going to be working with that comma as a separator, the delimiter between values. So let's jump into the code
and see what we can do here. So let's jump straight
into processing. We're going to once
again write a output , there's going to be a writer. We're going to call this
data.csv this time. As simple as that, we will
be creating a CSV file. Let's create a header. So output.printline. Here, our header, we have the value of x, y, red, green, blue. Notice that I'm adding
commas to all those files. This is just a simple string, but I'm thinking of these values that are separated by commas just because the CSV file is going to be able
to understand that. Let's imagine that what
do we want to record? We want to record
some variables, x and y are going to be
float point variables. Red, green, and blue are going to be
potentially integers. Let's do it for a series
of maybe 500 objects. So for i in range 500, and we're going to
create an x variable, it's going to be
random.randrange between zero and 1200 which is going to be
the size of our canvas. You can use this
canvas variable. I'm going to try to think that what I'm doing is
creating coordinates of let's say 500 random elements
or circles in the screen. We have our module import
random here available, so we can use the
random function. Make sure that you
have that as well. Down here, we're going to
do the same thing for y. In this case we're going
to use the random_height. Now, let's just do an r, this is going to start for red. Let's just copy paste
this line once more. In this case we
will have a value, but it's a random value
between zero and 255. That's for a random
red channel color. We can do the same thing for two more times for R, G, and B. So everything is
random at this point. If we would like to
see graphically, we can use fill for r, g,b so that we have a visual representation
of what we are doing. So we can do an ellipse
in the coordinates x, y, 20, 20. But what we're
actually trying to do is write all this
information to our file. We've seen this in
previous videos. We can actually use
random variables to construct 500 random
spheres or circle. Often the data that
we will obtain from outside might
not be random. So it's going to be probably
a lot more interesting data than the one that
we're creating here. But we're learning how
to write first a file, and then we're going to
learn how to read it. Here's where it could
actually get tricky, where we actually do
output.printline. This line we want to convert
to a string, the variable x. Then we want to add
to that a comma. Then we want to repeat
this sequence for all the different
variables we have. We could do that side by side
like this and do it for y. Some people really like seeing
it a little bit like this. So we have y, we have r, g, and b. So I really invited
you to format your documents in
the way that are the most readable for you, RGB. I sometimes sacrifice the amount of space the code might take. There we go. We're
closing that line. So that's the same print line as if we had everything
in sequence. We're just making sure
that we are adding the value as a string
with the comma for x, y, r, G, b and so on. So that is it for the output. Then we should be
within the loop here. Notice that in order to close the document,
what we have done before, which is output.flush,
and output.close, I need to get out of the loop. You don't want to be doing the closing of the
document within the loop, and this might be
a simple mistake because you're still
within the indentation. So make sure that you don't keep these two lines indented, therefore they exit the loop, and we the document at the end. I also want to make sure
that we do have a background because we're drawing these
ellipses in the screen. Let's just do a background
here, a black background. So we're not doing the
draw loop right now, we're just drawing 500 circles in the screen at random
locations. That's fine. That work. We can see
them and we should have in this point a CSV file. So I'm going to go into a text or a Google Sheets
document where we can open, let's just drag and
drop that CSV file. Once you load a CSV file, you'll see what you have here. What we have is first, it's going to be our header
row that contains the x, y. Basically what we described
in this line up here. This line became the
first line of our file, and as we continue
printing the values here Google Sheets automatically
can understand the CSV file to be a
comma separated values. Comma separated
value, meaning that these units end up in their
own individual cells. So we have data that could
be perfectly suitable for something like visualizing
this data if we wanted to reconstruct the
drawing from this data. Or maybe start doing like
a scatter plot or any form of data visualization that we might think might be
useful for this data. Coming to a file like this has a lot of clarity of these are x, y coordinates and these are the color values that are
associated with those. With this we're going to leave it here and
we're going to be looking at how to read this file in the next video.
I'll see you there.