science

Jagged array

Jagged array is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Jagged array rather than just read about it. In short: In computer science, a jagged array, also known as a ragged array or irregular array is an array of arrays of which the member arrays can be of different lengths, producing rows of jagged edges when visualized as output. In contrast, two-dimensional arrays are always rectangular so jagged arrays should not be confused with multidimensional arrays, but the former is often used to emulate the latter.

Key takeaways

Jagged array belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Jagged array to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Jagged array from memory before moving on to harder problems.

Reference excerpt

In computer science, a jagged array, also known as a ragged array or irregular array is an array of arrays of which the member arrays can be of different lengths, producing rows of jagged edges when visualized as output. In contrast, two-dimensional arrays are always rectangular so jagged arrays should not be confused with multidimensional arrays, but the former is often used to emulate the latter. Jagged array can be implemented with Iliffe vector data structure in languages such as Java, PHP, Python (multidimensional lists), Ruby, C#.NET, Visual Basic.NET, Perl, JavaScript, Objective-C, Swift, and Atlas Autocode.

Examples In C# and Java jagged arrays can be created with the following code:

In C and C++, a jagged array can be created (on the stack) using the following code:

In C/C++, jagged arrays can also be created (on the heap) with an array of pointers:

In C++/CLI, jagged array can be created with the code:

In Fortran, a jagged array can be created using derived types with allocatable component(s):

In Python, jagged arrays are not native but one can use list comprehensions to create a multi-dimensional list which supports any dimensional matrix:

See also Variable-length array Iliffe vector

References

Illustrations

Jagged array: Memory layout of a jagged array — Memory layout of a jagged array

Worked examples

Example 1 — a first encounter with Jagged array

Start with the simplest possible case. Write down what Jagged array claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Jagged array before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Jagged array ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Jagged array

In research: Jagged array appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Jagged array in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Jagged array is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arrays, so understanding it makes those chapters shorter.
In everyday life: Look for Jagged array outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Jagged array in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Jagged array means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Jagged array out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Jagged array in simple terms?

Why does Jagged array matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Jagged array?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Jagged array.