Create expressions using Power Fx

Power Fx is a low-code language that uses Excel-like formulas. Use Power Fx to create complex logic that allows your copilots to manipulate data. For instance, a Power Fx formula can set the value of a variable, parse a string, or use an expression in a condition. For more information, see the Power Fx overview and formula reference.

Note

Power Fx formulas in Copilot Studio use US-style numbering. That is, the decimal separator is a period or dot, as in 12,567.892. This means Power Fx parameters must be separated by commas (,).

Prerequisites

• Create and edit topics
• Work with variables

Use variables in a formula

To use a variable in a Power Fx formula, you must add a prefix to its name to indicate the variable's scope:

• For system variables, use System.
• For global variables, use Global.
• For topic variables, use Topic.

For example, to use the system variable Conversation.Id in a formula, refer to the system variable as System.Conversation.Id.

Use literal values in a formula

In addition to using variables in a Power Fx formula, you can enter literal values. To use a literal value in a formula, you must enter it in the format that corresponds to its type. The following table lists the data types and the format of their corresponding literal values.

Type	Format examples
String	"hi", "hello world!", "copilot"
Boolean	Only true or false
Number	1, 532, 5.258,-9201
Record and Table	[1], [45, 8, 2], ["cats", "dogs"], { id: 1 }, { message: "hello" }, { name: "John", info: { age: 25, weight: 175 } }
DateTime	Time(5,0,23), Date(2022,5,24), DateTimeValue("May 10, 2022 5:00:00 PM")
Choice	Not supported
Blank	Only Blank()

Common Power Fx formulas

The following table lists data types and corresponding Power Fx formulas to use with that data type.

Type	Power Fx formulas
String	Text function Concat and Concatenate functions Len function Lower, Upper, and Proper functions IsMatch, Match, and MatchAll functions EndsWith and StartsWith functions Find function Replace and Substitute function
Boolean	Boolean function And, Or, and Not functions If and Switch functions
Number	Decimal, Float, and Value functions Int, Round, RoundDown, RoundUp, and Trun functions
Record and Table	Concat and Concatenate functions Count, CountA, CountIf, and CountRows functions ForAll function First, FirstN, Index, Last, and LastN functions Filter, Search, and LookUp functions JSON function ParseJSON function
DateTime	Date, DateTime, and Time functions DateValue, TimeValue, and DateTimeValue functions Day, Month, Year, Hour, Minute, Second, and Weekday functions Now, Today, IsToday, UTCNow, UTCToday, IsUTCToday functions DateAdd, DateDiff, and TimeZoneOffset functions Text function
Blank	Blank, Coalesce, IsBlank, and IsEmpty functions Error, IfError, IsError, IsBlankOrError functions

Use Power Fx to set a variable

In this example, a Power Fx expression stores and outputs the customer's name in capital letters.

1. Create a topic and add a Question node.

2. For Enter a message, enter "What is your name?".

3. Under Identify, select the entity Person name.

4. Select the box under Save response as, and then select the variable Var1 and name it customerName.

5. Under the Question node, select + and then select Set a variable value.

6. Select the box under Set variable, and then select Create new and name it capsName.

7. In the To value box, select the > arrow, and then select the Formula tab.

8. In the fx box, enter Upper(Text(Topic.customerName)), and then select Insert.

   

9. Under the Question node, select + and then select Send a message.

10. Enter "HELLO ", select {x}, and then select capsName.

    

Use a Power Fx formula as a condition

To evaluate more complex expressions, set up Condition nodes to use Power Fx formulas.

In this example, the copilot determines if a booking date qualifies for a discount. To do that, it checks whether the booking date provided by the customer is 14 days or more from the current date.

1. Create a topic and add a Question node.

2. For Enter a message, enter "Booking date?".

3. Under Identify, select the entity Date and time.

4. Select the box under Save response as, and then select the variable Var1 and name it bookingDate.

   

5. Select the Add node icon below the Question node, and then select Add a condition.

6. Select the More icon (…) of the Condition node, and then select Change to formula.

7. In the Function box, select the > arrow, and then select the Formula tab.

8. Replace the contents of the fx box with the formula Topic.bookingDate > (DateAdd (Now(), 14)), and then select Insert.

9. Under the Condition node, add a Message node and enter the message "You qualify for a discount."

10. Under the All Other Conditions node, add a Message node and enter the message, "Sorry, you don't qualify for a discount."