Pattern Update Method: Iteratively updating each individual node

Question

Pattern Update Method: Iteratively updating each individual node

I'm struggling to grasp the concept of updating only those d3 nodes where the data has changed. Despite my efforts, I still can't seem to get it right. In the test example provided below, I am noticing that everything is being updated instead of just the required nodes.

Could it be possible that I am approaching this problem entirely wrong or am I simply making a small mistake?

In this particular example, clicking on a shape toggles its form between a circle and square while also updating a "clickCnt" property associated with it. Subsequently, the data is redrawn. Although the functionality partially works, it appears that everything is getting redrawn. Additionally, there seems to be an issue when clicking on the "red" shape even though the code is identical to that of the other shapes.

var nodeData = [];
nodeData.push({ "type": 'red', "shape": "circle", "clickCount": 0, x: 30, y: 100 });
nodeData.push({ "type": 'orange', "shape": "square", "clickCount": 0, x: 110, y: 100 });
nodeData.push({ "type": 'yellow', "shape": "circle", "clickCount": 0, x: 210, y: 100 });
nodeData.push({ "type": 'green', "shape": "square", "clickCount": 0, x: 310, y: 100 });

// Additional node data entries...

var width = 400;
var height = 400;

d3.select("div#svg-container").select("svg").remove();
var svg = d3.select("#svg-container").append("svg")
    .attr("width", width)
    .attr("height", height);

var content = svg.append("g")

function render(data) {
    var groups = content.selectAll("g")
        .data(data, function (d) {
            return d;
        });

    groups.exit().remove();

    groups.enter()
        .append("g")
        .attr('transform', function (d, i) {
            return 'translate(' + d.x + ',' + d.y + ')'
        })
        .each(function (d) {
            // Code for appending text, shapes, click handling, etc.
        });
}

render(nodeData);

function handleIconClick(evt) {
    if (evt.shape == "circle") {
        evt.shape = "square"
    } else if (evt.shape == "square") {
        evt.shape = "circle"
    }
    evt.clickCount++;

    document.getElementById('output').innerHTML = "Item clicked: " + evt.type + " " + evt.clickCount;
    
    render(nodeData);
}

    .circle {
      stroke: red;
      stroke-width: 2px;
      
    }
    .square {
      stroke: blue;
      stroke-width: 2px;
    }

    #timeline-background {
      background: slategray;
    }

    .label {
      fill: blue;
    }
    .small-text {
      font-size: 16px;
      
    }

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>

<body>
  <label id="output">out</label>
  <div id="timeline-background" style="width: 100%; height: 100%;">
    <div id="svg-container"></div>
  </div>
</body>

javascript d3.js

Answer 1

Answer №1

The issue you're facing stems from the key function used when binding your data.

According to the documentation, a key function can be utilized to determine which datum corresponds with each element, using a string identifier for each datum and element. However, in your case, instead of returning a string, you are returning an entire object:

var groups = content.selectAll("g")
    .data(data, function (d) {
        return d;
        //     ^--- this is an object
    });

This approach will not work as intended.

Consequently, you are observing the behavior where all groups in the exit selection are removed, followed by all elements being re-rendered in the enter selection.

To better illustrate this, interact with the elements and review the console output:

...

(partial) Solution: To rectify this issue, it's advised to use a unique string value, such as the label property:

var groups = content.selectAll("g")
    .data(data, function (d) {
        return d.label;
    });

Observe how this change impacts the visualization:

...

By implementing this adjustment, you'll notice that the exit selection size always remains zero.

However, keep in mind that this solution is considered partial because it does not address updating elements. Establishing an update selection falls outside the scope of this answer, leaving that task up to you.

Answer 2

The issue you're facing stems from the key function used when binding your data.

According to the documentation, a key function can be utilized to determine which datum corresponds with each element, using a string identifier for each datum and element. However, in your case, instead of returning a string, you are returning an entire object:

var groups = content.selectAll("g")
    .data(data, function (d) {
        return d;
        //     ^--- this is an object
    });

This approach will not work as intended.

Consequently, you are observing the behavior where all groups in the exit selection are removed, followed by all elements being re-rendered in the enter selection.

To better illustrate this, interact with the elements and review the console output:

...

(partial) Solution: To rectify this issue, it's advised to use a unique string value, such as the label property:

var groups = content.selectAll("g")
    .data(data, function (d) {
        return d.label;
    });

Observe how this change impacts the visualization:

...

By implementing this adjustment, you'll notice that the exit selection size always remains zero.

However, keep in mind that this solution is considered partial because it does not address updating elements. Establishing an update selection falls outside the scope of this answer, leaving that task up to you.

Pattern Update Method: Iteratively updating each individual node

Answer №1

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