WEBVTT 1 00:00:00.210 --> 00:00:01.460 Hi guys and welcome back. 2 00:00:01.460 --> 00:00:03.170 In this video, we're going to start learning 3 00:00:03.170 --> 00:00:04.870 about matplotlib and we're going 4 00:00:04.870 --> 00:00:06.990 to draw a simple line chart. 5 00:00:06.990 --> 00:00:08.123 So let's get started. 6 00:00:09.130 --> 00:00:11.030 To draw any graph or chart, 7 00:00:11.030 --> 00:00:12.890 we first need to create a figure. 8 00:00:12.890 --> 00:00:15.520 And inside a figure, we can draw graphs or charts. 9 00:00:15.520 --> 00:00:19.050 In matplotlib, these graphs or charts are called plots. 10 00:00:19.050 --> 00:00:21.600 And plots are drawn on top of axes, 11 00:00:21.600 --> 00:00:23.040 the plural for axis. 12 00:00:23.040 --> 00:00:25.810 Most plots are drawn on x- and y-axes, 13 00:00:25.810 --> 00:00:27.000 although some plots can be drawn 14 00:00:27.000 --> 00:00:29.020 on three-dimensional axes as well. 15 00:00:29.020 --> 00:00:30.950 We're gonna start by importing pyplot. 16 00:00:30.950 --> 00:00:34.940 So I'll do import matplotlib.pylot as plt. 17 00:00:34.940 --> 00:00:38.300 This is the standard import for matplotlib. 18 00:00:38.300 --> 00:00:42.490 Then to create a figure, we just do plt.figure. 19 00:00:42.490 --> 00:00:43.780 You can see that PyCharm is complaining 20 00:00:43.780 --> 00:00:45.830 that I have an unvalid import here 21 00:00:45.830 --> 00:00:48.000 because I haven't installed matplotlib yet, 22 00:00:48.000 --> 00:00:49.290 so let's do that. 23 00:00:49.290 --> 00:00:51.830 You can do this over in your terminal. 24 00:00:51.830 --> 00:00:54.620 Make sure that you have activated your virtual environment 25 00:00:54.620 --> 00:00:57.483 and then simply do pip instal matplotlib. 26 00:00:58.460 --> 00:01:01.780 And if this fails, you should upgrade pip first. 27 00:01:01.780 --> 00:01:03.060 But here you can see it passes 28 00:01:03.060 --> 00:01:05.610 and matplotlib is now installed. 29 00:01:05.610 --> 00:01:08.260 So the red line goes away. 30 00:01:08.260 --> 00:01:09.610 Now, after creating a figure, 31 00:01:09.610 --> 00:01:12.300 we can go ahead and plot inside that figure. 32 00:01:12.300 --> 00:01:16.480 So we can do plt.plot, one, two, three, four, for example, 33 00:01:16.480 --> 00:01:20.100 and three, five, nine, and 25. 34 00:01:20.100 --> 00:01:21.560 Now, running this, which I'm gonna do 35 00:01:21.560 --> 00:01:23.790 by right clicking and pressing on run 36 00:01:23.790 --> 00:01:25.180 is not going to do anything 37 00:01:25.180 --> 00:01:26.670 because we haven't told matplotlib 38 00:01:26.670 --> 00:01:28.960 to display the output produced. 39 00:01:28.960 --> 00:01:31.900 We can do that with plt.show. 40 00:01:31.900 --> 00:01:33.320 Now we can run this file again. 41 00:01:33.320 --> 00:01:37.070 I'm gonna click the green play icon at the top right 42 00:01:37.070 --> 00:01:38.350 and you can see that we get 43 00:01:38.350 --> 00:01:41.900 our matplotlib graph viewer here. 44 00:01:41.900 --> 00:01:43.440 A lot of this is not stuff 45 00:01:43.440 --> 00:01:44.820 that we've developed ourselves. 46 00:01:44.820 --> 00:01:47.530 We've just told matplotlib to draw this graph 47 00:01:47.530 --> 00:01:48.363 but it comes with matplotlib 48 00:01:48.363 --> 00:01:50.140 and it allows you to do things 49 00:01:50.140 --> 00:01:52.470 like pan around the axes, for example, 50 00:01:52.470 --> 00:01:53.560 and zoom in and out 51 00:01:53.560 --> 00:01:56.010 and do some configuration as well. 52 00:01:56.010 --> 00:01:59.460 Plt.plot is used to plot any arbitrary data. 53 00:01:59.460 --> 00:02:02.200 Is creates a 2D set of axes, 54 00:02:02.200 --> 00:02:04.300 and by default, it produces a line graph 55 00:02:04.300 --> 00:02:06.810 where these points are the x-coordinates 56 00:02:06.810 --> 00:02:09.310 and these points are the y-coordinates. 57 00:02:09.310 --> 00:02:12.170 And then it joins the points with a straight line. 58 00:02:12.170 --> 00:02:13.870 We can change it so that instead of joining the point 59 00:02:13.870 --> 00:02:14.810 with a straight line, 60 00:02:14.810 --> 00:02:17.480 it uses circles for the points let's say. 61 00:02:17.480 --> 00:02:19.260 We can do that with a third argument. 62 00:02:19.260 --> 00:02:21.530 I'm putting in the string o. 63 00:02:21.530 --> 00:02:24.180 If we do this, you'll see that we get circles now 64 00:02:24.180 --> 00:02:26.820 instead of a joined line. 65 00:02:26.820 --> 00:02:29.020 There's also a list of built-in colours 66 00:02:29.020 --> 00:02:31.410 that we can use to colour the circles or lines 67 00:02:31.410 --> 00:02:33.470 or anything else automatically. 68 00:02:33.470 --> 00:02:35.300 Here I'm using ko as the string 69 00:02:35.300 --> 00:02:37.083 to colour these circles black. 70 00:02:38.010 --> 00:02:40.050 K is the letter for the colour black 71 00:02:40.050 --> 00:02:41.820 because B is for blue. 72 00:02:41.820 --> 00:02:43.020 We can also get rid of that 73 00:02:43.020 --> 00:02:47.750 and assign the result of plt.plot to a variable, 74 00:02:47.750 --> 00:02:49.650 and that gives us the plot itself. 75 00:02:49.650 --> 00:02:52.300 The line or the points that we've drawn. 76 00:02:52.300 --> 00:02:54.650 Then we can do plt.setp 77 00:02:54.650 --> 00:02:56.330 and here we can pass in the plot, 78 00:02:56.330 --> 00:02:57.680 which is lines in our case, 79 00:02:57.680 --> 00:03:00.100 and then we can also change certain parameters. 80 00:03:00.100 --> 00:03:01.600 Here I'm gonna pass in colour, 81 00:03:01.600 --> 00:03:03.710 making use of the American spelling, 82 00:03:03.710 --> 00:03:07.440 and we can pass in a hexadecimal colour in there if we want 83 00:03:07.440 --> 00:03:10.383 and that allows us to use a custom colour if we prefer. 84 00:03:11.260 --> 00:03:13.030 As well as coordinates in the x-axis, 85 00:03:13.030 --> 00:03:14.900 we can use categorical variables. 86 00:03:14.900 --> 00:03:17.470 So here I'm going to make a couple of changes 87 00:03:17.470 --> 00:03:20.290 and instead of one, two, three and four in the x-axis, 88 00:03:20.290 --> 00:03:24.003 we're gonna plot, for example, Men, Women and Children. 89 00:03:25.010 --> 00:03:27.140 And then we can plot values against that. 90 00:03:27.140 --> 00:03:29.060 Naturally, these values will normally be coming 91 00:03:29.060 --> 00:03:31.260 from our database or some sort of file 92 00:03:31.260 --> 00:03:33.060 but here I'm just plotting arbitrary values 93 00:03:33.060 --> 00:03:34.850 but you can see that now we get these labels 94 00:03:34.850 --> 00:03:37.970 in the x-axis instead of the numbers. 95 00:03:37.970 --> 00:03:41.300 Matplotlib will automatically create even ticks, 96 00:03:41.300 --> 00:03:42.910 these things here are called ticks, 97 00:03:42.910 --> 00:03:45.360 if you rpovide numerical data. 98 00:03:45.360 --> 00:03:47.100 But if you provide categorical data, 99 00:03:47.100 --> 00:03:48.230 as we're doing here, 100 00:03:48.230 --> 00:03:50.460 then it will only show the ticks provided. 101 00:03:50.460 --> 00:03:52.780 Of course, it can't interpolate between men and women 102 00:03:52.780 --> 00:03:54.740 to give you a tick in the middle. 103 00:03:54.740 --> 00:03:55.610 As well as all this, 104 00:03:55.610 --> 00:03:57.040 which allows us to create the plot 105 00:03:57.040 --> 00:03:58.850 so we can also do a lot more. 106 00:03:58.850 --> 00:04:01.970 For example, provide labels for the x and y-axis 107 00:04:01.970 --> 00:04:04.760 or provide a title for the plot itself. 108 00:04:04.760 --> 00:04:07.330 We can do that with plt.xlabel 109 00:04:07.330 --> 00:04:09.290 and this allows us to define, for example, 110 00:04:09.290 --> 00:04:10.970 a label for the x-axis. 111 00:04:10.970 --> 00:04:14.400 Plt.ylabel allows us to define a label for the y-axis. 112 00:04:14.400 --> 00:04:16.550 I'm gonna set it to Amount here 113 00:04:16.550 --> 00:04:18.990 and plt.title allows us to define a title 114 00:04:18.990 --> 00:04:20.873 that appears above the chart. 115 00:04:23.600 --> 00:04:25.440 I'll run this to show you what it looks like 116 00:04:25.440 --> 00:04:27.260 and you can see that we've got our labels here 117 00:04:27.260 --> 00:04:29.090 at the bottom and at the left 118 00:04:29.090 --> 00:04:30.520 and our title at the top. 119 00:04:30.520 --> 00:04:31.730 All right, that's everything for this video. 120 00:04:31.730 --> 00:04:32.950 Thank you guys for joining me, 121 00:04:32.950 --> 00:04:34.453 I'll see you in the next one.