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.

Overview

Modifiers create synthetic variations of a base ticker without a separate data source for each scenario. For example, you can model questions like "What if SPY had 0.9% annual expenses?" or "What if I applied 2x leverage to VTI?" The transforms are applied before the backtest engine runs, so all downstream modeling (e.g. tax calculations) uses the modified returns.

Paste a testfol.io expression into the import bar in the modifier modal, and ArthaPilot parses it and fills the matching fields automatically (mapping ticker names where needed).

You configure modifiers per-ticker via the modification icon next to the ticker input.

Button to open the modifier modal, located next to 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.

For leverage modifiers, financing uses a collateral-netting model: long leverage pays the financing rate on borrowed capital, while inverse and sub-1x exposure earn the financing rate on cash collateral. SW controls swap notional for the spread term; it is not the financing rate itself.

Base ticker: any supported ticker symbol (e.g. SPY, VTI.SIM, 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.

Click on the modification chip to copy the ticker expression.

Modifier Reference

All available modifier keys, grouped by category:

Key	Name	Description
`L`	Leverage	Daily-rebalanced leverage factor (e.g. 2 for 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 (e.g. 0.9 = 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 (e.g. 0.05 = +5% cap)
`CL`	Cap Low	Minimum daily return (e.g. -0.05 = -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

Modifiers are applied in a fixed canonical order, regardless of the order they appear in the expression. This ensures consistent results:

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 final leveraged series)

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 and can be used anywhere a regular ticker is accepted.

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.

Research tickers are stored per-user. Free accounts can save up to 5; Pro is unlimited. Each ticker stores its full definition, so the underlying transforms or source references are always reproducible.

Save a modified ticker as a research ticker for reuse — Save a modified ticker as a research ticker from the modification modal.

Examples

SPY?L=2&E=0.9: 2x daily-leveraged SPY with 0.9% annual expense ratio
VTI?FB=(VTI.SIM): VTI with history extended backward using VTI.SIM data
QQQ?UR=0.10&UV=0.15: QQQ scaled to 10% CAGR and 15% annualized volatility
SPY?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)