Ticker modifiers & research tickers
Ticker modifiers let you apply mathematical transforms to a ticker's daily returns before backtesting. They use testfol.io-compatible expression syntax, so you can import expressions directly from testfol.io or share them with other tools.
On this page
Overview
Modifiers create synthetic variations of a base ticker without a separate data source for each scenario. For example, you can ask, "What if SPY had 0.9% annual expenses?" You can also ask, "What if I applied 2x leverage to VTI?" The engine applies the transforms before the backtest runs. Thus, all downstream modeling, such as tax calculations, uses the modified returns.
Type or paste a testfol.io name or expression into any ticker input, then press Enter. ArthaPilot resolves the name to its own ticker, moves the parameters into the modifier fields, and shows the result in the input and its chip. The import bar in the modifier modal accepts the same expressions.
| You paste | ArthaPilot shows |
|---|---|
TQQQSIM | TQQQ.SIM |
SPYTR | SPY.SIM |
QQQSIM?L=3&E=0.91 | QQQ.SIM with 3x leverage and a 0.91% expense ratio |
TLT?FB=VUSTX&FBE=0.05 | TLT filled backward with VUSTX at a 0.05% expense ratio |
A name ArthaPilot does not carry stays in the input with an error, so you can replace it. Each input takes one ticker. A testfol.io share link or a list such as SPYSIM 60, TLTSIM 40 does not import. Add one position for each ticker.
Signed-out visitors can use a core set of .SIM tickers. Plans and limits lists them. Every other .SIM ticker needs a free account.
You configure modifiers per-ticker via the modification icon next to the ticker input.
Expression syntax
A modifier expression follows the pattern TICKER?KEY=VALUE&KEY=VALUE. For example, SPY?L=2&E=0.9 applies 2x daily leverage and a 0.9% expense ratio to SPY.
Leverage modifiers use a collateral-netting model. Long leverage pays the financing rate on borrowed capital. Inverse and sub-1x exposure earn it on cash collateral. SW controls swap notional, not the financing rate.
- Base ticker: any supported ticker symbol, such as SPY, VTI.SIM, or UPRO
- Parameters: key=value pairs joined by
&, appended after? - Nested expressions: some parameters accept a ticker expression as their value, wrapped in parentheses. For example,
SPY?FB=(VTI.SIM)fills backward using VTI.SIM data
You can copy a ticker expression by clicking on the chip next to the ticker symbol.
Modifier reference
All available modifier keys, grouped by category:
| Key | Name | Description |
|---|---|---|
L | Leverage | Daily-rebalanced leverage factor. For example, 2 means 2x. |
SW | Swap Exposure | Swap notional used for the spread term of leverage financing |
SP | Swap Spread | Spread over risk-free rate for leverage financing |
E | Expense Ratio | Annual expense ratio subtracted daily. For example, 0.9 means 0.9%. |
UE | Undo Expense | Add back an embedded expense ratio before other transforms |
FB | Fill-Backward | Extend history by splicing another ticker's data before inception (accepts nested expression) |
FBE | Fill-Backward Expense | Expense adjustment applied only to the fill-backward portion |
UR | Return Target | Scale returns to achieve a target annualized CAGR |
UV | Volatility Target | Scale returns to achieve a target annualized volatility |
UC | Correlation Target | Adjust returns to target correlation with the base series (requires seed) |
DB | De-Beta | Target beta relative to a reference ticker |
DBREF | De-Beta Reference | Reference ticker for de-beta (accepts nested expression) |
CU | Cap Up | Maximum daily return. For example, 0.05 sets a +5% cap. |
CL | Cap Low | Minimum daily return. For example, -0.05 sets a -5% floor. |
SD | Seed | Random seed for reproducible stochastic transforms |
BK | Block Size | Number of trading days per shuffle block |
BL | Block Low | Minimum random block size |
BH | Block High | Maximum random block size |
BR | Block Replacement | Sample blocks with replacement (1) or without (0) |
BO | Block Overlap | Allow overlapping blocks (1) or not (0) |
BREF | Block Reference | Shuffle using another ticker's return blocks (accepts nested expression) |
Application order
The engine applies modifiers in a fixed canonical order, regardless of the order they appear in the expression. This keeps results consistent:
- FB / FBE: fill-backward history extension (applied first so all subsequent transforms operate on the full extended series)
- UE: undo embedded expense (restores gross-of-fee returns before applying custom costs)
- BK / BL / BH / BR / BO: shuffle blocks (randomizes return order while preserving terminal value)
- UC: correlation targeting (adjusts returns to hit a target correlation)
- UR / UV: return and volatility targets
- DB / DBREF: de-beta adjustment
- CU / CL: daily return caps
- L / SW / SP: leverage with financing costs (applied late so it leverages the already-transformed series)
- E: expense ratio subtraction (applied last so costs reflect the series after leverage)
Bond tickers
Synthetic bond tickers use the B! prefix with yield-curve and maturity parameters. For example, B!Y=0.04&M=10 creates a 10-year bond at a flat 4% yield.
- Y: flat yield (cannot combine with YL/YH)
- YL / YH: yield curve low/high for curve-aware mode
- M: target maturity in years (required)
- C: coupon type: "C" for coupon-bearing, "Z" for zero-coupon
- E: expense ratio on the synthetic bond
Research tickers
You can save any modifier expression as a reusable research ticker. In the modifier modal, configure your desired transforms, then click “Save Ticker” and give it a name. Research tickers appear in autocomplete suggestions. You can use them anywhere a regular ticker works.
You can also create research tickers backed by a saved portfolio or strategy from Workspace. These resolve to the portfolio or strategy return series over the requested date range.
ArthaPilot stores research tickers per user. Free accounts can save up to 5. Pro accounts have no limit. Each ticker stores its full definition, so the underlying transforms or source references are always reproducible.
Examples
SPY?L=2&E=0.9: 2x daily-reset SPY with 0.9% annual expense ratioVTI?FB=(VTI.SIM): VTI with history extended backward using VTI.SIM dataQQQ?UR=0.10&UV=0.15: QQQ scaled to 10% CAGR and 15% annualized volatilitySPY?CU=0.05&CL=-0.05: SPY with daily returns capped at +/-5%SPY?SD=42&BK=21: SPY with 21-day return blocks shuffled (seed 42 for reproducibility)SPY?DB=0&DBREF=(AGG): SPY de-betaed to zero against AGG (market-neutral)