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 the same class-dominance rules as cat(...,1). Real integer mixtures preserve the leftmost participating integer class with saturating conversion.
• 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.
• Compatible host and resident numeric inputs use the owning provider when possible; otherwise RunMat gathers exact values, concatenates on the host, and restores the result when the owner can preserve its class.

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)

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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