vertcat — Concatenate inputs vertically along the first dimension with MATLAB semicolon semantics.

vertcat(A1, A2, ...) stacks inputs top-to-bottom along dimension 1, equivalent to MATLAB semicolon syntax [A1; A2; ...] with compatible shape rules.

Syntax

B = vertcat()
B = vertcat(A1, An...)

Inputs

Returns

Errors

How vertcat works

• Hard-codes dim = 1. All inputs must agree on every dimension except the first.
• Accepts numeric, logical, complex, character, string, and cell arrays with MATLAB-compatible type checking. Mixing classes is an error.
• Scalars are treated as 1×1, enabling concise row-building such as vertcat(1, 2, 3).
• Empty inputs participate naturally. If any shared dimension is zero, the result is empty with the expected shape.
• The optional trailing 'like', prototype pair forces the output to match the prototype's data residency (CPU vs GPU) and numeric flavour.
• Mixing gpuArray inputs with host inputs is disallowed. Convert explicitly via gpuArray or gather to control residency.

Does RunMat run vertcat on the GPU?

vertcat delegates to cat(dim = 1, …). When the active acceleration provider implements the cat hook, concatenation happens entirely on the GPU, keeping gpuArray inputs resident and avoiding costly round-trips. Providers that lack this hook trigger a transparent fallback: RunMat gathers the operands to the host, concatenates them with MATLAB semantics, and uploads the result back to the originating device so downstream code still sees a gpuArray. This mirrors MATLAB's explicit GPU workflows while keeping RunMat's auto-offload planner informed.

Examples

Stacking matrices by adding rows

A = [1 2; 3 4];
B = [5 6; 7 8];
C = vertcat(A, B)

Expected output:

C =
     1     2
     3     4
     5     6
     7     8

Building a column vector from scalars

col = vertcat(1, 2, 3, 4)

Expected output:

col =
     1
     2
     3
     4

Combining character arrays into taller text blocks

top = ['RunMat'];
bottom = ['Rocks!'];
banner = vertcat(top, bottom)

Joining string arrays into multi-row tables

header = ["Name" "Score"];
rows = ["Alice" "98"; "Bob" "92"];
table = vertcat(header, rows)

Preserving logical masks when stacking

mask1 = logical([1 0 1]);
mask2 = logical([0 1 0]);
stacked = vertcat(mask1, mask2)

Extending cell arrays downwards

row1 = {1, "low"};
row2 = {2, "high"};
grid = vertcat(row1, row2)

Keeping gpuArray inputs resident on the device

G1 = gpuArray(rand(128, 256));
G2 = gpuArray(rand(64, 256));
stacked = vertcat(G1, G2)

Requesting GPU output with the 'like' prototype

proto = gpuArray.zeros(1, 3);
result = vertcat([1 2 3], [4 5 6], "like", proto)

Working with empty rows without surprises

empty = zeros(0, 3);
combo = vertcat(empty, empty)

Stacking complex matrices preserves imaginary parts

z1 = complex([1 2], [3 4]);
z2 = complex([5 6], [7 8]);
joined = vertcat(z1, z2)

Using vertcat with coding agents

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

Related Array functions

Open-source implementation

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

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

About RunMat

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