lower — Convert text to lowercase in MATLAB and RunMat.

lower(text) converts alphabetic characters in text to lowercase. Supported text containers and non-alphabetic pass-through behavior follow MATLAB semantics.

Syntax

out = lower(str)

Inputs

Returns

Errors

How lower works

• String inputs stay as strings. String arrays preserve their size, orientation, and missing values.
• Character arrays are processed row by row. The result remains a rectangular char array; if any row grows after lowercasing (for example because 'İ' expands), the array widens and shorter rows are padded with spaces.
• Cell arrays must contain string scalars or character vectors. The result is a cell array of the same size with each element converted to lowercase, and other types raise MATLAB-compatible errors.
• Missing string scalars (string(missing)) remain missing and are returned as <missing>.
• Inputs that are numeric, logical, structs, or GPU tensors raise MATLAB-compatible type errors.

Does RunMat run lower on the GPU?

lower executes on the CPU. When the input (or any nested element) resides on the GPU, RunMat gathers it to host memory before performing the conversion so results remain identical to MATLAB. Providers do not need to implement custom kernels for this builtin.

GPU memory and residency

RunMat automatically keeps string data on the host for now. If text originates from GPU-based computations (for example as numeric code points stored on the device), lower gathers those values before applying the transformation, so you never need to call gpuArray explicitly for this builtin.

Examples

Convert A String Scalar To Lowercase

txt = "RunMat";
result = lower(txt)

Expected output:

result = "runmat"

Lowercase Each Element Of A String Array

labels = ["NORTH" "South"; "EaSt" "WEST"];
lowered = lower(labels)

Expected output:

lowered = 2×2 string
    "north"    "south"
    "east"     "west"

Lowercase Character Array Rows While Preserving Shape

animals = char("CAT", "DOGE");
result = lower(animals)

Expected output:

result =

  2×4 char array

    'cat '
    'doge'

Lowercase A Cell Array Of Character Vectors

C = {'HELLO', 'World'};
out = lower(C)

Expected output:

out = 1×2 cell array
    {'hello'}    {'world'}

Keep Missing Strings As Missing

vals = string(["DATA" "<missing>" "GPU"]);
converted = lower(vals)

Expected output:

converted = 1×3 string
    "data"    <missing>    "gpu"

Lowercase Text Stored On A GPU Input

codes = gpuArray(uint16('RUNMAT'));
txt = char(gather(codes));
result = lower(txt)

Expected output:

result = 'runmat'

Using lower with coding agents

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

FAQ

Related Strings functions

Open-source implementation

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

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

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