How to provide constant value for y?

[ManavalanG]

Is there a way to provide a constant value to y-axis in the bar chart (and others as well)? For example, in the gallery example of bar chart, is it possible to a set constant value 0.0005 to y instead of reading specifying it from the data object?

[manzt]

Thanks for the question! I assume you mean fixing the min/max of the y-axis so that it is not locally determined from the data. This can be accomplished using the domain property on the y encoding.

import gosling as gos

data = gos.multivec(
    url="https://resgen.io/api/v1/tileset_info/?d=UvVPeLHuRDiYA3qwFlm7xQ",
    row="sample",
    column="position",
    value="peak",
    categories=["sample 1"],
    binSize=5,
)

track = gos.Track(data).mark_bar().encode(
    x="start:G",
    xe="end:G",
--  y="peak:Q",
++  y=gos.Y("peak:Q", domain=[0, 0.0005]),
    stroke=gos.value("white"),
    strokeWidth=gos.value(0.5),
).properties(layout="linear", width=725, height=180)

track.view(title="Basic Marks: Bar", subtitle="Tutorial Examples")

[ManavalanG]

Thanks for the quick response. Sorry my question wasn't clear.

Using the input bed file (an example below), I would like to draw a bar chart and the bars should have a constant y value of 5 where ymin=0 and ymax=20, for example,.

#chrom  start   end size_mb
chr2    188576793   189661479   1.08
chr6    34145900    35787881    1.64
chr6    111096151   112132983   1.04

I can't use pandas because of HPC limitations to manipulate this data to add another column and then supply it to gosling. Also, due to system limitations, I would not be able to add a column to this file, save it to disk and then load it to gosling. So I wonder if I can directly supply this constant value to gosling for Y.

I also looked into data transform but didn't find a solution.

[sehilyi]

Hi @ManavalanG, you could set the top and bottom positions of bars with constant px values using y and ye (link to the JS online editor-(G'y4(GCpeakKWOK'axisNrightK'domain4%5B0J20%5DG)G)G%5Djsize4(I5)6)6%5D%0A)%20%20-%2CG4!%206%0A9'JWC'fieldNG6*I'value4J%2C%20K'-N4'OquantitativeW'typeNX'tracks4%5BZamplej-'~9genomic'%01~jZXWONKJIGC964-*_))

"height": 100,
...
"y": { "value": 0 }, // baseline
"ye": { "value": 25 } // 1/4 of the height

Is this what you were looking for?

Also, just curious since you want to set the 'constant' height of the bars – is actual data, i.e, size_mb, used for other visual channels, like color, in your use case?

[ManavalanG]

Thanks @sehilyi I thought y and ye take discrete values and didn't realize they are instead fractional (or %).

Also, just curious since you want to set the 'constant' height of the bars – is actual data, i.e, size_mb, used for other visual channels, like color, in your use case?

I wanted to highlight 3-4 features in a genomic region using overlay (couldn't use stack to avoid certain complexity), and I wanted to highlight one of the features with a particular color up to a particular y value. I couldn't figure it out using y/ye and finally ended up using arrow marks instead to highlight the feature; If I ever need to refactor it, I will use your solution :)