8000 remove the visible call of `glue` in the saving section by lheagy · Pull Request #109 · UBC-DSCI/introduction-to-datascience-python · GitHub
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remove the visible call of glue in the saving section #109

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29 changes: 15 additions & 14 deletions source/viz.md
Original file line number Diff line number Diff line change
Expand Up @@ -508,7 +508,7 @@ visualization. Let's create a scatter plot using the `altair`
package with the `waiting` variable on the horizontal axis, the `eruptions`
variable on the vertical axis, and the `mark_point` geometric object.
By default, `altair` draws only the outline of each point. If we would
like to fill them in, we pass the argument `filled=True` to `mark_point`. In
like to fill them in, we pass the argument `filled=True` to `mark_point`. In
place of `mark_point(filled=True)`, we can also use `mark_circle`.
The result is shown in {numref}`faithful_scatter`.

Expand Down Expand Up @@ -1225,9 +1225,9 @@ The plot in {numref}`islands_plot_sorted` is now a very effective
visualization for answering our original questions. Landmasses are organized by
their size, and continents are colored differently than other landmasses,
making it quite clear that continents are the largest seven landmasses.
We can make one more finishing touch in {numref}`islands_plot_titled`: we will
We can make one more finishing touch in {numref}`islands_plot_titled`: we will
add a title to the chart by specifying `title` argument in the `alt.Chart` function.
Note that plot titles are not always required; usually plots appear as part
Note that plot titles are not always required; usually plots appear as part
of other media (e.g., in a slide presentation, on a poster, in a paper) where
the title may be redundant with the surrounding context.

Expand Down Expand Up @@ -1353,10 +1353,10 @@ Note that
*vertical lines* are used to denote quantities on the *horizontal axis*,
while *horizontal lines* are used to denote quantities on the *vertical axis*.

To add the dashed line on top of the histogram, we
**add** the `mark_rule` chart to the `morley_hist`
To add the dashed line on top of the histogram, we
**add** the `mark_rule` chart to the `morley_hist`
using the `+` operator.
Adding features to a plot using the `+` operator is known as *layering* in `altair`.
Adding features to a plot using the `+` operator is known as *layering* in `altair`.
This is a very powerful feature of `altair`; you
can continue to iterate on a single plot object, adding and refining
one layer at a time. If you stored your plot as a named object
Expand Down Expand Up @@ -1446,7 +1446,7 @@ To fix this issue we can convert the `Expt` variable into a `nominal`
(i.e., categorical) type variable by adding a suffix `:N`
to the `Expt` variable. Adding the `:N` suffix ensures that `altair`
will treat a variable as a categorical variable, and
hence use a discrete color map in visualizations.
hence use a discrete color map in visualizations.
We also specify the `stack=False` argument in the `y` encoding so
that the bars are not stacked on top of each other.

Expand Down Expand Up @@ -1831,8 +1831,8 @@ perfectly re-created when loading and displaying, with the hope that the change
is not noticeable. *Lossless* formats, on the other hand, allow a perfect
display of the original image.

- *Common file types:*
- [JPEG](https://en.wikipedia.org/wiki/JPEG) (`.jpg`, `.jpeg`): lossy, usually used for photographs
- *Common file types:*
- [JPEG](https://en.wikipedia.org/wiki/JPEG) (`.jpg`, `.jpeg`): lossy, usually used for photographs
- [PNG](https://en.wikipedia.org/wiki/Portable_Network_Graphics) (`.png`): lossless, usually used for plots / line drawings
- [BMP](https://en.wikipedia.org/wiki/BMP_file_format) (`.bmp`): lossless, raw image data, no compression (rarely used)
- [TIFF](https://en.wikipedia.org/wiki/TIFF) (`.tif`, `.tiff`): typically lossless, no compression, used mostly in graphic arts, publishing
Expand All @@ -1845,8 +1845,8 @@ display of the original image.
objects (lines, surfaces, shapes, curves). When the computer displays the image, it
redraws all of the elements using their mathematical formulas.

- *Common file types:*
- [SVG](https://en.wikipedia.org/wiki/Scalable_Vector_Graphics) (`.svg`): general-purpose use
- *Common file types:*
- [SVG](https://en.wikipedia.org/wiki/Scalable_Vector_Graphics) (`.svg`): general-purpose use
- [EPS](https://en.wikipedia.org/wiki/Encapsulated_PostScript) (`.eps`), general-purpose use (rarely used)
- *Open-source software:* [Inkscape](https://inkscape.org/)

Expand Down Expand Up @@ -1875,7 +1875,7 @@ Let's learn how to save plot images to `.png` and `.svg` file formats using the
`faithful_scatter_labels` scatter plot of the [Old Faithful data set](https://www.stat.cmu.edu/~larry/all-of-statistics/=data/faithful.dat)
{cite:p}`faithfuldata` that we created earlier, shown in {numref}`faithful_scatter_labels`.
To save the plot to a file, we can use the `save`
method. The `save` method takes the path to the filename where you would like to
method. The `save` method takes the path to the filename where you would like to
save the file (e.g., `img/filename.png` to save a file named `filename.png` to the `img` directory).
The kind of image to save is specified by the file extension. For example, to
create a PNG image file, we specify that the file extension is `.png`. Below
Expand All @@ -1891,6 +1891,7 @@ faithful_scatter_labels.save("img/faithful_plot.svg")
```

```{code-cell} ipython3
:tags: [remove-cell]
import os
import numpy as np
png_size = np.round(os.path.getsize("img/faithful_plot.png")/(1024*1024), 2)
Expand All @@ -1916,9 +1917,9 @@ glue("svg_size", svg_size)
```

Take a look at the file sizes in {numref}`png-vs-svg-table`
Wow, that's quite a difference! In this case, the `.png` image is almost 4 times
Wow, that's quite a difference! In this case, the `.png` image is almost 4 times
smaller than the `.svg` image. Since there are a decent number of points in the plot,
the vector graphics format image (`.svg`) is bigger than the raster image (`.png`), which
the vector graphics format image (`.svg`) is bigger than the raster image (`.png`), which
just stores the image data itself.
In {numref}`png-vs-svg`, we show what
the images look like when we zoom in to a rectangle with only 3 data points.
Expand Down
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