Command-line interface

The principle-viz command runs the calculations of this manual from the shell and prints the result as JSON; --output also writes it to a file. It draws no figures. Install it as a tool (Installing the command-line tool), or prefix each command with uv run inside a project.

principle-viz equilibrium \
  --demand-intercept 10 --demand-slope -1 \
  --supply-intercept 2 --supply-slope 1

{
  "q_star": 4.0,
  "p_star": 6.0,
  "is_valid_market": true,
  "notes": []
}

Market arguments

Most commands describe the market by two lines in inverse form, \(p = a + b Q\):

--demand-intercept

Price intercept \(a\) of demand.

--demand-slope

Slope \(b\) of demand.

--supply-intercept

Price intercept \(a\) of supply.

--supply-slope

Slope \(b\) of supply.

--output

Also write the JSON to this file, creating its directory.

Commands

CLI commands lists the calculation and options of each command; the calculation of each is described in its chapter.

equilibrium

Linear equilibrium

Section — Linear markets

shift

Comparative statics: --demand-delta-intercept, --demand-delta-slope, --supply-delta-intercept, --supply-delta-slope

Section — Comparative statics

discrete

Discrete market: --demand-values, --supply-values, --price-rule {midpoint,lower,upper}

Section — Discrete markets

elasticity

Point elasticity: --intercept, --slope, --quantity; arc elasticity with --q1, --p1

Section — Elasticity and total revenue

revenue

Elasticity and revenue schedule: --samples

Section — Elasticity and total revenue

welfare

Surplus: --policy {baseline,tax,subsidy,control} with the options of that policy

Section — Welfare

report-dwl

One-row DWL report: --policy {tax,subsidy,control}, --csv

Section — Welfare

tax

--tax-type {fixed,per_unit,ad_valorem}, --amount, --tax-on {consumer,producer}

Section — Taxes and subsidies

subsidy

--amount, --subsidy-to {consumer,producer}

Section — Taxes and subsidies

controls

--control-type {ceiling,floor}, --control-price

Section — Price controls

trade

--world-price, --tariff, --import-quota, --quota-rent-recipient

Section — International trade

externality

--external-cost, --external-benefit

Section — Market failures

common-resource

--congestion-cost

Section — Market failures

public-good

--benefit-intercepts, --benefit-slopes, --cost-intercept, --cost-slope, --samples

Section — Market failures

minimum-wage

--labor-demand-*, --labor-supply-*, --minimum-wage

Section — Labor and loanable funds

loanable-funds

--savings-*, --investment-*, --savings-shift, --investment-shift, --government-borrowing

Section — Labor and loanable funds

ppf

--x-intercept, --y-intercept, --curvature, --x-good, --y-good, --x-growth, --y-growth, --samples

Section — Production possibilities

principle-viz <command> --help lists every option of a command.

principle-viz tax \
  --demand-intercept 10 --demand-slope -1 \
  --supply-intercept 2 --supply-slope 1 \
  --tax-type per_unit --amount 1 --tax-on producer

The output holds the untaxed equilibrium (baseline_equilibrium), the taxed one (post_tax) and the changes, as compare_tax_scenario() returns them. Here the quantity is 3.5, the consumer price 6.5 and the producer price 5.5.

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