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# Deep Dive: Understanding math and substring formula for custom exports

Stevie LaFortune
Expensify Team Posts:

**221**Expensify Team*The more you know - - - *

*The more you know - - -*

*Information about the current user exporting the reports. This is useful if you need to print the name of the exporter. *

*To export the email of the currently logged in Expensify user -*

**{user:email}**would output [email protected] assuming that is the currently logged in Expensify user's email.

**{user:email|frontPart}**would output bob assuming that is the currently logged in Expensify user's email.

*You are able to add formulas that are a math type, allowing you to do arbitrary mathematical equations in your export.*

- * — Multiplication {math: 3 * 4} output 12

- / — Division {math: 3 / 4 }output 0.75

- + — Addition {math: 3 + 4 }output

- - — Subtraction {math: 3 - 4 }output -1

- ^ — Exponent {math: 3 ^ 4 } output 81

- sqrt — The square root of a number. {sqrt:64} output 8
**Note**- You can also combine the value of any two numerical fields. For example, you can use {math: {expense:tag:glcode} + {expense:category:glcode}} to add the value of the Tag GL code with the Category GL code.

**Substring formulas will output a subset of the string in question. It is important to remember that the count starts at 0 not 1.**

`<strong>{expense:merchant|substr:0:4}</strong>`

would output`Star`

for a merchant named Starbucks. This is because we are telling it to start at position 0 and be of 4 character length.

`<strong>{expense:merchant|substr:4:5}</strong>`

would output`bucks`

for a merchant named Starbucks. This is because we are telling it to start at position 4 and be of 5 character length.

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