topic Re: Code Review: Set polyline M-values to cumulative length of line in ArcGIS Pro Questions

Arcade Code Review: Set polyline M-values to cumulative length of line

Bud — Fri, 24 Jun 2022 02:40:31 GMT

I have an Arcade calculation attribute rule that sets polyline M-values to the cumulative length of the line.

The script works as expected. But I'm still a novice, so I thought I'd ask: Can the script be improved?

Notes about the script:

- It works for both singlepart and multipart features.
- It densifies true curves (unavoidable, since Arcade pre-densifies true curves).
- The code below is out-of-date. I've posted an updated version in a reply...further down in this post.

//var paths = [[[0, 5, null], [10, 10, null], [30, 0, null], [50, 10, null], [60, 10, null]]];  //JS

//Only do the calculation if the geometry was changed/edited.
if (!Equals(Geometry($feature), Geometry($originalfeature))) { 
    var geom = Dictionary(Text(Geometry($feature))); 
    var paths = geom['paths']; 

    //Alternatively, this could be done with the Arcade distance() function. I chose to do the math manually so that the script can be used elsewhere, such as VSCode (for debugging).
    function pythagoras(x1, y1, x2, y2) {
        return sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
    }
    for (var path_idx in paths) {
        var oldX = paths[0][0][0], oldY = paths[0][0][1], length = 0;
        for (var point_idx in paths[path_idx]) {
            var newX = paths[path_idx][point_idx][0], newY = paths[path_idx][point_idx][1];
            length += pythagoras(oldX, oldY, newX, newY);
            paths[path_idx][point_idx][2] = length;
            oldX = newX;
            oldY = newY;
        }
    }  
    console(paths);
    return { "result": { "geometry": Polyline(geom) } };

    //Output: [[[0,5,0],[10,10,11.180339887498949],[30,0,33.54101966249685],[50,10,55.90169943749475],[60,10,65.90169943749476]]]
}

(The script was adapted from this GitHub sample: Set Ms to Index.)

Thanks!

Re: Code Review: Set polyline M-values to cumulative length of line

MikeMillerGIS — Sun, 13 Mar 2022 12:16:18 GMT

Looks pretty good, minor tweaks and comments

//Only do the calculation if the geometry was changed/edited.
// I like to exit early when condition is not met, makes the code a little more readable
if (Equals(Geometry($feature), Geometry($originalfeature))) { 
    return
}
var geom = Dictionary(Text(Geometry($feature))); 
var paths = geom['paths']; 

//Alternatively, this could be done with the Arcade distance() function. I chose to do the math manually so that the script can be used elsewhere, such as VSCode (for debugging).
function pythagoras(x1, y1, x2, y2) {
    return sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
}

// Easier to read when on multi lines and moved out of the loop, it was being reset on each part, not sure that is what you wanted
var oldX = paths[0][0][0];
var oldY = paths[0][0][1];
// dont use length, that is a reserved function name
var line_length = 0;

for (var path_idx in paths) {
    for (var point_idx in paths[path_idx]) {
        var newX = paths[path_idx][point_idx][0];
        var newY = paths[path_idx][point_idx][1];
        line_length += pythagoras(oldX, oldY, newX, newY);
        // can use a negative slice, will work when there is no Z
        paths[path_idx][point_idx][-1] = line_length;
        oldX = newX;
        oldY = newY;
    }
}  
console(paths);
return { "result": { "geometry": Polyline(geom) } };

//Output: [[[0,5,0],[10,10,11.180339887498949],[30,0,33.54101966249685],[50,10,55.90169943749475],[60,10,65.90169943749476]]]
}  
//Generic JS version: https://jsfiddle.net/5m1c69g3/

Re: Code Review: Set polyline M-values to cumulative length of line

Bud — Mon, 14 Mar 2022 12:23:37 GMT

Thanks very much Mike. That really helps.

Re: Code Review: Set polyline M-values to cumulative length of line

Bud — Mon, 21 Mar 2022 15:56:27 GMT

Hi Mike, here's my latest version, in case you're interested. I used your suggestions.

//Script title: Set polyline M-values to cumulative length of line var geom = Dictionary(Text(Geometry($feature))); var paths = geom['paths']; //Using the Equals() function doesn't work as expected. See: Arcade: Editing M-values not treated as change to geometry (https://community.esri.com/t5/arcgis-pro-questions/arcade-editing-m-values-not-treated-as-change-to/m-p/1153917) //if (Equals(Geometry($feature), Geometry($originalfeature)) ) { if (Text(Geometry($feature)) == Text(Geometry($originalfeature))) { console("The geometry has not changed. We don't need to redefine the M-Values.") return } else { //Alternatively, this could be done with the Arcade distance() function. I chose to do the math manually so that the script can be used elsewhere, such as VSCode (for debugging). function pythagoras(x1, y1, x2, y2) { return sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2)); } var oldX = paths[0][0][0]; var oldY = paths[0][0][1]; var line_length = 0; for (var path_idx in paths) { for (var point_idx in paths[path_idx]) { var newX = paths[path_idx][point_idx][0]; var newY = paths[path_idx][point_idx][1]; //For multi-part features, we want the M-value for additional parts to start at the last M-value from the last part. We don't want to measure the distance *between* parts. //So, for the first vertex in a given part, we will skip calculating the length between vertices. if (point_idx != 0) { line_length += pythagoras(oldX, oldY, newX, newY); } //We can use a negative slice: it will work when there is no Z. paths[path_idx][point_idx][-1] = line_length; oldX = newX; oldY = newY; } } console("The geometry has changed. So we *will* redefine the M-Values.") return { "result": { "geometry": Polyline(geom) } }; }

@JohannesLindner might find this interesting.

Cheers!

Re: Code Review: Set polyline M-values to cumulative length of line

MikeMillerGIS — Mon, 21 Mar 2022 19:50:29 GMT

The else is redundant, easier to read without the indent

//Script title: Set polyline M-values to cumulative length of line var geom = Dictionary(Text(Geometry($feature))); var paths = geom['paths']; //Using the Equals() function doesn't work as expected. See: Arcade: Editing M-values not treated as change to geometry (https://community.esri.com/t5/arcgis-pro-questions/arcade-editing-m-values-not-treated-as-change-to/m-p/1153917) //if (Equals(Geometry($feature), Geometry($originalfeature)) ) { if (Text(Geometry($feature)) == Text(Geometry($originalfeature))) { console("The geometry has not changed. We don't need to redefine the M-Values.") return } //Alternatively, this could be done with the Arcade distance() function. I chose to do the math manually so that the script can be used elsewhere, such as VSCode (for debugging). function pythagoras(x1, y1, x2, y2) { return sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2)); } var oldX = paths[0][0][0]; var oldY = paths[0][0][1]; var line_length = 0; for (var path_idx in paths) { for (var point_idx in paths[path_idx]) { var newX = paths[path_idx][point_idx][0]; var newY = paths[path_idx][point_idx][1]; //For multi-part features, we want the M-value for additional parts to start at the last M-value from the last part. We don't want to measure the distance *between* parts. //So, for the first vertex in a given part, we will skip calculating the length between vertices. if (point_idx != 0) { line_length += pythagoras(oldX, oldY, newX, newY); } //We can use a negative slice: it will work when there is no Z. paths[path_idx][point_idx][-1] = line_length; oldX = newX; oldY = newY; } } console("The geometry has changed. So we *will* redefine the M-Values.") return { "result": { "geometry": Polyline(geom) } };

Re: Code Review: Set polyline M-values to cumulative length of line

JohannesLindner — Tue, 22 Mar 2022 06:41:20 GMT

Looks good!

As Mike said, the else is unnecessary and makes it a little harder to read. Personally, I would declare geom and paths right before oldX, so that they are closer to where you actually use them.

Re: Code Review: Set polyline M-values to cumulative length of line

Bud — Fri, 25 Mar 2022 08:37:03 GMT

Thanks. Good suggestion about the variables. I tried to clean them up:

Re: Code Review: Set polyline M-values to cumulative length of line

MikeMillerGIS — Fri, 25 Mar 2022 08:49:10 GMT

You could use the https://developers.arcgis.com/arcade/function-reference/geometry_functions/#equals function to compare Geo instead of a text comparison.

Re: Code Review: Set polyline M-values to cumulative length of line

Bud — Fri, 25 Mar 2022 10:01:22 GMT

Yeah, although Equals() doesn’t work the way I would have expected…it doesn’t consider changes to M-values: Arcade: Editing M-values not treated as change to geometry

So that’s why I went with the text comparison.

Re: Code Review: Set polyline M-values to cumulative length of line

MikeMillerGIS — Fri, 25 Mar 2022 10:05:30 GMT

Ahh good point, forgot about that.

Re: Arcade Code Review: Set polyline M-values to cumulative length of line

Bud — Fri, 31 Mar 2023 02:00:37 GMT

It looks like someone posted a similar script on GitHub:

Create SetMValues
https://github.com/Esri/arcade-expressions/pull/72/commits/7a6c0c824dfc3ee24252a7a6dd57556875589399

I wonder what this comment refers to:

This Arcade expression will calculates field values from intersecting point layer

Does the attribute rule actually do that? I’m a bit rusty on Arcade.

Re: Arcade Code Review: Set polyline M-values to cumulative length of line

JohannesLindner — Fri, 31 Mar 2023 05:29:29 GMT

No, it doesn't. I guess they copied the rule template and forgot to delete the comment.

Re: Arcade Code Review: Set polyline M-values to cumulative length of line

Bud — Fri, 12 Jul 2024 14:56:01 GMT

Re: Arcade Code Review: Set polyline M-values to cumulative length of line

Bud — Wed, 29 Jan 2025 15:35:57 GMT

For future reference, when my organization moves from Pro 2.6.8 to Pro 3.x:

...copy your geoemtry(can do this by calling Dictionary(geo) on it, prior to 3.2, you need to call Dictionary(Text(geo))).

Arcade modify only Z geometry

Re: Arcade Code Review: Set polyline M-values to cumulative length of line

Bud — Wed, 29 Jan 2025 15:35:37 GMT

A related Arcade solution: How to batch edit Z values and set them all to zero