Numbers ISOMITTED: Missing LAMBDA Inputs, Zero and Defaults

• Introduced: The original introduction release and date are not established by the checked references. LAMBDA’s separately documented introduction does not establish this helper’s first release.
• Availability: Currently documented in Apple’s Functions Help 15.4 documentation edition; no final supported-version endpoint is established.
• Scope: Shared iWork reference. Function-specific historical Mac, iPad, iPhone and iCloud endpoints are unverified.
• Checked: October 14, 2026, against the official ISOMITTED reference. Examples were independently calculated; no native Numbers test was performed.

ISOMITTED(parameter)

The official ISOMITTED reference defines this test in the context of LAMBDA and LAMBDA.APPLY. The parameter is the name defined inside LAMBDA, such as temp; it is not a cell address to substitute blindly.

For a one-parameter calculation, the two patterns are:

=LAMBDA.APPLY(A2,LAMBDA(temp,ISOMITTED(temp)))
=LAMBDA.APPLY(,LAMBDA(temp,ISOMITTED(temp)))

The first supplies A2. The second deliberately leaves the first input slot empty, before the comma. That omitted-slot form follows Apple’s example. Do not delete the comma and move LAMBDA into the value’s position.

Create OmissionLab, with eight columns A:H and eight rows, including one header row. Label A1:D1 Fahrenheit, Omitted?, Celsius and Direct Celsius. Enter 70,0,32,-40 in A2:A5.

In B2 enter =LAMBDA.APPLY(A2,LAMBDA(temp,ISOMITTED(temp))) and fill through B5. In C2 enter:

=LAMBDA.APPLY(A2,LAMBDA(temp,IF(ISOMITTED(temp),"value is missing",(temp-32)*5/9)))

Fill C2 through C5. In D2 enter =(A2-32)*5/9 and fill through D5 for a direct numeric control.

The first row reproduces Apple’s supplied-70 example. Row 3 is especially useful: passing zero does not select the missing-value message, and zero Fahrenheit is not zero Celsius.

Put labels in E2:E4 and the following formulas in F2:F4:

F3 reproduces the omitted case in the official entry. The quotation marks belong in the formula, where they delimit text; the resulting message does not contain those quotation marks. F4 supplies a literal zero rather than an empty input slot.

The IF branch chooses a text message for omission and a numeric conversion for a supplied number. A downstream numeric summary should not silently treat those messages as actual temperature observations.

Create DefaultReading, with eight columns A:H and eight rows, including one header row. Put headers Supplied reading, Omitted?, Effective reading, Doubled reading and Numeric control in A1:E1. Enter 0,10,25,-5,100 in A2:A6.

• B2: =LAMBDA.APPLY(A2,LAMBDA(reading,ISOMITTED(reading)))
• C2: =LAMBDA.APPLY(A2,LAMBDA(reading,IF(ISOMITTED(reading),100,reading)))
• D2: =LAMBDA.APPLY(A2,LAMBDA(reading,IF(ISOMITTED(reading),100,reading)*2))
• E2: =A2*2

Fill B2:E2 through row 6. All B results are FALSE. C contains 0,10,25,-5,100, and D:E contain 0,20,50,-10,200. The negative input stays negative: this example demonstrates presence, not a nonnegative-data rule.

In G2 enter =LAMBDA.APPLY(,LAMBDA(reading,IF(ISOMITTED(reading),100,reading))) for 100. In G3 enter =LAMBDA.APPLY(,LAMBDA(reading,IF(ISOMITTED(reading),100,reading)*2)) for 200. G2 selects the default, while C6 also equals 100 because the caller explicitly supplied 100. Matching numeric results do not establish the same omission status.

Compare C2=0 with G2=100. A rule such as “use 100 whenever the value is zero” would incorrectly replace the deliberate zero in A2. ISOMITTED answers whether the parameter was supplied, allowing zero to remain a valid input.

The chosen default is part of this example’s calculation. It is not a built-in default of ISOMITTED or LAMBDA.APPLY, and a suitable default depends on your own worksheet’s meaning.

• Keep the test inside the LAMBDA whose parameter you are checking. The current entry does not establish ISOMITTED as a general blank-cell detector.
• A reference to an empty cell, an empty string, an error or a missing imported value is not the explicit omitted-slot fixture above. Their conversion and evaluation details remain unverified here.
• Apple’s LAMBDA reference says definitions are local to their cell and cannot be nested. Each example uses one local definition; filling a formula copies that definition.
• A bare LAMBDA definition returns an error according to Apple. Use LAMBDA.APPLY to supply or intentionally omit its input and obtain a result; the checked entries do not establish every exact malformed-formula error token.
• The examples use English function names, decimal points and commas. Apple’s functions overview specifies semicolons between arguments when the decimal separator is a comma. Preserve the intentional empty slot when adapting punctuation.

LAMBDA defines the parameter and calculation. LAMBDA.APPLY passes inputs, and IF selects the message or default.