`startsWith` — Test whether text values start with specified prefixes using MATLAB-compatible broadcasting and case options.

startsWith(str, pattern) returns logical results indicating whether each text element begins with a corresponding prefix. It supports MATLAB-compatible string, char, and cellstr containers plus implicit expansion rules.

Syntax

tf = startsWith(str, pat)
tf = startsWith(str, pat, ignoreCase)
tf = startsWith(str, pat, "IgnoreCase", value)
tf = startsWith(str, pat, nameValuePairs...)

Inputs

Name	Type	Required	Default	Description
`str`	`Any`	Yes	—	Text input (string/char/cell/string array).
`pat`	`Any`	Yes	—	Pattern text (string/char/cell/string array).
`ignoreCase`	`Any`	Yes	`false`	Logical flag controlling case-sensitive matching.
`name`	`StringScalar`	Yes	`"IgnoreCase"`	Option name (`"IgnoreCase"`).
`value`	`Any`	Yes	—	Option value for `"IgnoreCase"`.
`nameValuePairs...`	`Any`	Variadic	—	Name-value option pairs (`"IgnoreCase"`, value).

Returns

Name	Type	Description
`tf`	`LogicalArray`	Logical result indicating whether each text element starts with the pattern.

Errors

Identifier	When	Message
`RunMat:startsWith:InvalidInput`	Text or pattern input is not a supported text container.	`startsWith: text and pattern inputs must be text values`
`RunMat:startsWith:InvalidOption`	IgnoreCase option arguments are invalid or malformed.	`startsWith: invalid option arguments`
`RunMat:startsWith:ShapeMismatch`	Text and pattern inputs are not broadcast-compatible.	`startsWith: input sizes are not broadcast-compatible`
`RunMat:startsWith:InternalError`	Internal logical result assembly failed.	`startsWith: internal error`

How `startsWith` works

Accepts text inputs as string scalars/arrays, character vectors/arrays, or cell arrays of character vectors.
Accepts patterns in the same formats; scalar inputs expand across the other argument following MATLAB broadcast rules.
Missing strings (<missing>) never match any pattern.
Empty patterns ("" or '') always match non-missing text elements.
Patterns that are <missing> never match and therefore return false.
Character arrays treat each row as an independent element; zero-row character arrays yield empty outputs.
MATLAB-compatible mode accepts the documented 'IgnoreCase', logicalValue name-value form. RunMat mode additionally accepts positional, numeric, textual, and resident scalar flag forms behind explicit compatibility extensions.
All eight integer classes are read exactly as RunMat-only IgnoreCase controls: zero is false and every nonzero value is true.
Returns a logical scalar when the broadcasted size is one element, otherwise returns a logical array.

Does RunMat run `startsWith` on the GPU?

startsWith performs host-side prefix comparison. Numeric resident values in text roles reject without provider access; admitted automatic controls gather, and explicit controls require RunMat mode.

GPU memory and residency

startsWith executes on host text. Automatic placement remains transparent for an admitted scalar control, while explicit gpuArray intent is compatibility-gated before gather.

Examples

Determine whether a string starts with a prefix

tf = startsWith("RunMat Accelerate", "RunMat")

Expected output:

tf = logical
   1

Perform a case-insensitive prefix check

tf = startsWith("RunMat", "run", 'IgnoreCase', true)

Expected output:

tf = logical
   1

Ignoring case with a positional flag

tf = startsWith("RUNMAT", "run", true)

Expected output:

tf = logical
   1

Apply a scalar prefix to every element of a string array

labels = ["alpha" "beta" "gamma"];
tf = startsWith(labels, "a")

Expected output:

tf = 1×3 logical array
   1   0   0

Match element-wise prefixes with implicit expansion

names = ["hydrogen"; "helium"; "lithium"];
prefixes = ["hyd"; "hel"; "lit"];
tf = startsWith(names, prefixes)

Expected output:

tf = 3×1 logical array
   1
   1
   1

Test prefixes for a cell array of character vectors

C = {'Mercury', 'Venus', 'Mars'};
tf = startsWith(C, 'M')

Expected output:

tf = 1×3 logical array
   1   0   1

Provide multiple prefixes as a column vector

tf = startsWith("saturn", ['s'; 'n'; 'x'])

Expected output:

tf = 3×1 logical array
   1
   0
   0

Handle empty and missing values

texts = ["", "<missing>"];
tf = startsWith(texts, "")

Expected output:

tf = 1×2 logical array
   1   0

Using `startsWith` with coding agents

Open a RunMat example with live inputs, then ask the agent to explain how startsWith changes the result.

Run a small startsWith example, explain the result, then change one input and compare the output.

FAQ

What types can I pass to startsWith?⌄

Use string scalars/arrays, character vectors/arrays, or cell arrays of character vectors for both arguments. Mixed combinations are accepted, and RunMat performs MATLAB-style implicit expansion when the array sizes differ.

How do I ignore letter case?⌄

For MATLAB-compatible code, supply 'IgnoreCase', true. RunMat mode also accepts textual, numeric, positional, and resident scalar extensions; the default remains case-sensitive.

What happens with empty patterns?⌄

Empty patterns ("" or '') always match non-missing text elements. When the text element is missing (<missing>), the result is false.

Can I provide multiple prefixes at once?⌄

Yes. Provide pattern as a string array, character array, or cell array of character vectors. RunMat applies implicit expansion so that scalar inputs expand across the other argument automatically.

How are missing strings treated?⌄

Missing string scalars (displayed as <missing>) never match any pattern and produce false in the result. Use ismissing if you need to handle missing values separately.

Does startsWith run on the GPU?⌄

No. Text and pattern values are host-only. Automatically placed scalar controls can gather transparently, while explicitly resident controls are admitted only by the RunMat compatibility extension.

Does startsWith preserve the input shape?⌄

Yes. The output is a logical array whose shape reflects the MATLAB-style implicit expansion result. When that shape contains exactly one element, the builtin returns a logical scalar.

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how startsWith is executed, line by line, in Rust.

View the source for startsWith in Rust on GitHub
Learn how the RunMat runtime works
Found a bug? Open an issue with a minimal reproduction.

About RunMat

RunMat is an open-source runtime that executes MATLAB-syntax code blazing on any GPU. It is licensed under the Apache 2.0 license.

RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
Start running code in seconds. RunMat runs in the browser, on the desktop, or from the CLI. No license server, no IT ticket.

Getting started · Benchmarks · Pricing

`startsWith` — Test whether text values start with specified prefixes using MATLAB-compatible broadcasting and case options.

Syntax

tf = startsWith(str, pat)
tf = startsWith(str, pat, ignoreCase)
tf = startsWith(str, pat, "IgnoreCase", value)
tf = startsWith(str, pat, nameValuePairs...)

Inputs

Name	Type	Required	Default	Description
`str`	`Any`	Yes	—	Text input (string/char/cell/string array).
`pat`	`Any`	Yes	—	Pattern text (string/char/cell/string array).
`ignoreCase`	`Any`	Yes	`false`	Logical flag controlling case-sensitive matching.
`name`	`StringScalar`	Yes	`"IgnoreCase"`	Option name (`"IgnoreCase"`).
`value`	`Any`	Yes	—	Option value for `"IgnoreCase"`.
`nameValuePairs...`	`Any`	Variadic	—	Name-value option pairs (`"IgnoreCase"`, value).

Returns

Name	Type	Description
`tf`	`LogicalArray`	Logical result indicating whether each text element starts with the pattern.

Errors

Identifier	When	Message
`RunMat:startsWith:InvalidInput`	Text or pattern input is not a supported text container.	`startsWith: text and pattern inputs must be text values`
`RunMat:startsWith:InvalidOption`	IgnoreCase option arguments are invalid or malformed.	`startsWith: invalid option arguments`
`RunMat:startsWith:ShapeMismatch`	Text and pattern inputs are not broadcast-compatible.	`startsWith: input sizes are not broadcast-compatible`
`RunMat:startsWith:InternalError`	Internal logical result assembly failed.	`startsWith: internal error`

How `startsWith` works

Accepts text inputs as string scalars/arrays, character vectors/arrays, or cell arrays of character vectors.
Accepts patterns in the same formats; scalar inputs expand across the other argument following MATLAB broadcast rules.
Missing strings (<missing>) never match any pattern.
Empty patterns ("" or '') always match non-missing text elements.
Patterns that are <missing> never match and therefore return false.
Character arrays treat each row as an independent element; zero-row character arrays yield empty outputs.
MATLAB-compatible mode accepts the documented 'IgnoreCase', logicalValue name-value form. RunMat mode additionally accepts positional, numeric, textual, and resident scalar flag forms behind explicit compatibility extensions.
All eight integer classes are read exactly as RunMat-only IgnoreCase controls: zero is false and every nonzero value is true.
Returns a logical scalar when the broadcasted size is one element, otherwise returns a logical array.

Does RunMat run `startsWith` on the GPU?

startsWith performs host-side prefix comparison. Numeric resident values in text roles reject without provider access; admitted automatic controls gather, and explicit controls require RunMat mode.

GPU memory and residency

startsWith executes on host text. Automatic placement remains transparent for an admitted scalar control, while explicit gpuArray intent is compatibility-gated before gather.

Examples

Determine whether a string starts with a prefix

tf = startsWith("RunMat Accelerate", "RunMat")

Expected output:

tf = logical
   1

Perform a case-insensitive prefix check

tf = startsWith("RunMat", "run", 'IgnoreCase', true)

Expected output:

tf = logical
   1

Ignoring case with a positional flag

tf = startsWith("RUNMAT", "run", true)

Expected output:

tf = logical
   1

Apply a scalar prefix to every element of a string array

labels = ["alpha" "beta" "gamma"];
tf = startsWith(labels, "a")

Expected output:

tf = 1×3 logical array
   1   0   0

Match element-wise prefixes with implicit expansion

names = ["hydrogen"; "helium"; "lithium"];
prefixes = ["hyd"; "hel"; "lit"];
tf = startsWith(names, prefixes)

Expected output:

tf = 3×1 logical array
   1
   1
   1

Test prefixes for a cell array of character vectors

C = {'Mercury', 'Venus', 'Mars'};
tf = startsWith(C, 'M')

Expected output:

tf = 1×3 logical array
   1   0   1

Provide multiple prefixes as a column vector

tf = startsWith("saturn", ['s'; 'n'; 'x'])

Expected output:

tf = 3×1 logical array
   1
   0
   0

Handle empty and missing values

texts = ["", "<missing>"];
tf = startsWith(texts, "")

Expected output:

tf = 1×2 logical array
   1   0

Using `startsWith` with coding agents

Open a RunMat example with live inputs, then ask the agent to explain how startsWith changes the result.

Run a small startsWith example, explain the result, then change one input and compare the output.

FAQ

What types can I pass to startsWith?⌄

How do I ignore letter case?⌄

For MATLAB-compatible code, supply 'IgnoreCase', true. RunMat mode also accepts textual, numeric, positional, and resident scalar extensions; the default remains case-sensitive.

What happens with empty patterns?⌄

Empty patterns ("" or '') always match non-missing text elements. When the text element is missing (<missing>), the result is false.

Can I provide multiple prefixes at once?⌄

Yes. Provide pattern as a string array, character array, or cell array of character vectors. RunMat applies implicit expansion so that scalar inputs expand across the other argument automatically.

How are missing strings treated?⌄

Missing string scalars (displayed as <missing>) never match any pattern and produce false in the result. Use ismissing if you need to handle missing values separately.

Does startsWith run on the GPU?⌄

No. Text and pattern values are host-only. Automatically placed scalar controls can gather transparently, while explicitly resident controls are admitted only by the RunMat compatibility extension.

Does startsWith preserve the input shape?⌄

Yes. The output is a logical array whose shape reflects the MATLAB-style implicit expansion result. When that shape contains exactly one element, the builtin returns a logical scalar.

Search

contains · endsWith · matches · strfind

Text Analytics

Transform

Core

Pattern

digitsPattern · lettersPattern · pattern · regexpPattern · textBoundary · wildcardPattern

Regex

regexp · regexpi · regexprep

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how startsWith is executed, line by line, in Rust.

View the source for startsWith in Rust on GitHub
Learn how the RunMat runtime works
Found a bug? Open an issue with a minimal reproduction.

About RunMat

RunMat is an open-source runtime that executes MATLAB-syntax code blazing on any GPU. It is licensed under the Apache 2.0 license.

RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
Start running code in seconds. RunMat runs in the browser, on the desktop, or from the CLI. No license server, no IT ticket.

Getting started · Benchmarks · Pricing

startsWith — Test whether text values start with specified prefixes using MATLAB-compatible broadcasting and case options.

Syntax

Inputs

Returns

Errors

How startsWith works

Does RunMat run startsWith on the GPU?

GPU memory and residency

Examples

Determine whether a string starts with a prefix

Perform a case-insensitive prefix check

Ignoring case with a positional flag

Apply a scalar prefix to every element of a string array

Match element-wise prefixes with implicit expansion

Test prefixes for a cell array of character vectors

Provide multiple prefixes as a column vector

Handle empty and missing values

Using startsWith with coding agents

FAQ

Related Strings functions

Search

Text Analytics

Transform

Core

Pattern

Regex

Open-source implementation

About RunMat

Download RunMat

startsWith — Test whether text values start with specified prefixes using MATLAB-compatible broadcasting and case options.

Syntax

Inputs

Returns

Errors

How startsWith works

Does RunMat run startsWith on the GPU?

GPU memory and residency

Examples

Determine whether a string starts with a prefix

Perform a case-insensitive prefix check

Ignoring case with a positional flag

Apply a scalar prefix to every element of a string array

Match element-wise prefixes with implicit expansion

Test prefixes for a cell array of character vectors

Provide multiple prefixes as a column vector

Handle empty and missing values

Using startsWith with coding agents

FAQ

Related Strings functions

Search

Text Analytics

Transform

Core

Pattern

Regex

Open-source implementation

About RunMat

Download RunMat

`startsWith` — Test whether text values start with specified prefixes using MATLAB-compatible broadcasting and case options.

How `startsWith` works

Does RunMat run `startsWith` on the GPU?

Using `startsWith` with coding agents

`startsWith` — Test whether text values start with specified prefixes using MATLAB-compatible broadcasting and case options.

How `startsWith` works

Does RunMat run `startsWith` on the GPU?

Using `startsWith` with coding agents