Diff from "Building an Animated Line Chart with d3, React and Framer Motion" https://www.youtube.com/watch?v=kPbRDn5Fg0Y

chart-with-d3.jsx

import * as d3 from "d3";
import {
  eachMonthOfInterval,
  endOfMonth,
  format,
  isSameMonth,
  parseISO,
  startOfMonth,
} from "date-fns";
import useMeasure from "react-use-measure";
import { motion } from "framer-motion";
import estimatedMax from "~/utils/estimated-max";

export default function Chart({ entries }) {
  let [ref, bounds] = useMeasure();

  if (
    !entries
      .flatMap((entry) => entry.sets)
      .some((set) => set.reps > 0 && set.tracked)
  ) {
    return (
      <div className="flex h-full w-full items-center justify-center">
        <p className="text-sm italic text-gray-400">
          Add a tracked set to see a chart!
        </p>
      </div>
    );
  }

  let data = [...entries]
    .sort((a, b) => (a.date > b.date ? 1 : -1))
    .map((entry) => {
      let setWithHighestEstimatedMax = entry.sets
        .filter((set) => set.reps > 0 && set.tracked)
        .sort((a, b) => estimatedMax(b) - estimatedMax(a))[0];

      return {
        date: parseISO(entry.date),
        estimatedMax: setWithHighestEstimatedMax
          ? estimatedMax(setWithHighestEstimatedMax)
          : null,
      };
    })
    .filter((s) => s.estimatedMax);

  return (
    <div className="relative h-full w-full" ref={ref}>
      {bounds.width > 0 && (
        <ChartInner data={data} width={bounds.width} height={bounds.height} />
      )}
    </div>
  );
}

function ChartInner({ data, width, height }) {
  let margin = {
    top: 10,
    right: 10,
    bottom: 20,
    left: 24,
  };

  let startDay = startOfMonth(data.at(0).date);
  let endDay = endOfMonth(data.at(-1).date);
  let months = eachMonthOfInterval({ start: startDay, end: endDay });

  let xScale = d3
    .scaleTime()
    .domain([startDay, endDay])
    .range([margin.left, width - margin.right]);

  let yScale = d3
    .scaleLinear()
    .domain(d3.extent(data.map((d) => d.estimatedMax)))
    .range([height - margin.bottom, margin.top]);

  let line = d3
    .line()
    .x((d) => xScale(d.date))
    .y((d) => yScale(d.estimatedMax));
  let d = line(data);

  return (
    <>
      <svg className="" viewBox={`0 0 ${width} ${height}`}>
        {/* X axis */}
        {months.map((month, i) => (
          <g
            key={month}
            className="text-gray-400"
            transform={`translate(${xScale(month)},0)`}
          >
            {i % 2 === 1 && (
              <rect
                width={xScale(endOfMonth(month)) - xScale(month)}
                height={height - margin.bottom}
                fill="currentColor"
                className="text-gray-100"
              />
            )}
            <text
              x={(xScale(endOfMonth(month)) - xScale(month)) / 2}
              y={height - 5}
              textAnchor="middle"
              fill="currentColor"
              className="text-[10px]"
            >
              {format(month, "MMM")}
            </text>
          </g>
        ))}

        {/* Y axis */}
        {yScale.ticks(5).map((max) => (
          <g
            transform={`translate(0,${yScale(max)})`}
            className="text-gray-400"
            key={max}
          >
            <line
              x1={margin.left}
              x2={width - margin.right}
              stroke="currentColor"
              strokeDasharray="1,3"
            />
            <text
              alignmentBaseline="middle"
              className="text-[10px]"
              fill="currentColor"
            >
              {max}
            </text>
          </g>
        ))}

        {/* Line */}
        <motion.path
          initial={{ pathLength: 0 }}
          animate={{ pathLength: 1 }}
          transition={{ duration: 1.5, type: "spring" }}
          d={d}
          fill="none"
          stroke="currentColor"
          strokeWidth="2"
        />

        {/* Circles */}
        {data.map((d, i) => (
          <motion.circle
            key={d.date}
            r="5"
            cx={xScale(d.date)}
            cy={yScale(d.estimatedMax)}
            fill="currentColor"
            strokeWidth={2}
            stroke={
              months.findIndex((m) => isSameMonth(m, d.date)) % 2 === 1
                ? "#f5f5f4"
                : "white"
            }
          />
        ))}
      </svg>
    </>
  );
}

Oh should have in-lined that – here it is, you can just replace the import with this:

export default function estimatedMax(set) {
  if (+set.reps <= 0) {
    return 0;
  }

  // Jim Wendler formula
  return +set.weight * +set.reps * 0.0333 + +set.weight;
}

It's specific to the project, it's not a React thing btw :) Lemme know if that makes sense!

i tried replacing it and this is the error im getting

TypeError
Cannot assign to read only property 'message' of object 'SyntaxError: /src/index.js: Only one default export allowed per module. (21:0)

19 | }
20 |

21 | export default function Chart({ entries }) {
| ^
22 | let [ref, bounds] = useMeasure();
23 |
24 | if ('

this is the original error before replacing it :

ModuleNotFoundError
Could not find module in path: '~/utils/estimated-max' relative to '/src/index.js'
▶ 3 stack frames were collapsed.
$csb$eval
/src/index.js:12
9 | } from "date-fns";
10 | import useMeasure from "react-use-measure";
11 | import { motion } from "framer-motion";

12 | import estimatedMax from "~/utils/estimated-max";
13 |
14 | export default function Chart({ entries }) {
15 | let [ref, bounds] = useMeasure();