Work with curves

A curve is a precondition whose value varies by date. Declare dated points and choose step or linear interpolation.

import { cashflow, currencies, defineModel, entity, inflow, input, periods, schedule } from "deccf";

const occupancy = input.curve([
  { date: "2026-01", value: 0.75 },
  { date: "2026-07", value: 0.9 },
], { kind: "fraction", interpolation: "linear" });

const building = entity.asset();
const rent = cashflow({
  owner: building,
  direction: inflow,
  schedule: schedule.monthly(),
  amount: (ctx) => 20_000 * ctx.get(occupancy),
});
const model = defineModel({
  name: "occupancy-rent-curve",
  currency: currencies.SEK,
  timeline: periods.monthly({ from: "2026-01", count: 12 }),
  preconditions: { occupancy },
  entities: { building },
  flows: { rent },
});
return model;

step holds the latest point until the next one. linear interpolates between adjacent points. ctx.get(occupancy) reads the value at the current period date; ctx.curveAt(occupancy, date) reads it at an explicit date.

A run can replace a declared curve without changing the model:

import { cashflow, currencies, defineModel, entity, inflow, input, periods, run, schedule } from "deccf";

const building = entity.asset();
const occupancy = input.curve([
  { date: "2026-01", value: 0.75 },
  { date: "2026-07", value: 0.9 },
], { kind: "fraction", interpolation: "linear" });
const rent = cashflow({
  owner: building,
  direction: inflow,
  schedule: schedule.monthly(),
  amount: (ctx) => 20_000 * ctx.get(occupancy),
});
const model = defineModel({
  name: "occupancy-rent-curve",
  currency: currencies.SEK,
  timeline: periods.monthly({ from: "2026-01", count: 12 }),
  preconditions: { occupancy },
  entities: { building },
  flows: { rent },
});
const result = run(model, {
  deterministic: {
    inputs: {
      occupancy: {
        series: {
          points: [
            { date: "2026-01", value: 0.8 },
            { date: "2026-10", value: 0.95 },
          ],
          interpolation: "linear",
        },
        source: { note: "updated forecast" },
      },
    },
  },
});
return model;

A curve must contain at least one point, and its dates and values are validated. A scalar override cannot replace a curve input.