Multidimensional array vs array of records (1 Viewer)

[SadCeliac]

What's the difference and how would I explain what each one does??

Also what is an example of each? I would say that a grid or table can be represented by a 2D array, but I'm not sure what array of records do.

Thanks!

 

[cossine]

multidimensional array is array with 2 or more dimension. For each dimension you will need to provide a index if you want to access an element. So an example would be an RGB image. 1st dimension row, 2nd dimension column, 3rd dimension the channel (e.g. R, G or B).

When you say array of records that makes me think of the rows of a dataframe (dataframe is just fancy word for table of data). I guess another possibility would be a list containing a Python dictionaries. e.g. [{name:"XYZ", age: 9}, {name:"NMJ", age: 14}].

 

[SadCeliac]

multidimensional array is array with 2 or more dimension. For each dimension you will need to provide a index if you want to access an element. So an example would be an RGB image. 1st dimension row, 2nd dimension column, 3rd dimension the channel (e.g. R, G or B).

When you say array of records that makes me think of the rows of a dataframe (dataframe is just fancy word for table of data). I guess another possibility would be a list containing a Python dictionaries. e.g. [{name:"XYZ", age: 9}, {name:"NMJ", age: 14}].

Okay

Because I had this come up in a practice trial today and the answers said that array of records is ordered as well? Is that correct?

 

[cossine]

Okay

Because I had this come up in a practice trial today and the answers said that array of records is ordered as well? Is that correct?

So array is generally ordered i.e. order of the elements matter. That is depending on the index you pass you will get a different element.

So in example we gave

arr_records = [{name:"XYZ", age: 9}, {name:"NMJ", age: 14}]

print(arr_records[0]) will output {name:"XYZ", age: 9}.
print(arr_records[1]) will output {name:"NMJ", age: 14}

In contrast if you working with a set data type order will not matter. This is due to how sets are defined inmathematics. i.e. {1, 2} = {2, 1}

 

[wizzkids]

What's the difference and how would I explain what each one does??

Also what is an example of each? I would say that a grid or table can be represented by a 2D array, but I'm not sure what array of records do.

Thanks!

When you set up a multidimension array, you have to initialise "dim" the array and define explicitly how many dimensions it will hold and what data types it will hold. Then sufficient memory will be reserved to hold this size of array. It could be a 4-dimensional array.
Then you can read or write any element by addressing the appropriate values for each dimension. So you can see this is a fast way of randomly accessing an element.
An array of records sounds more like a flat-file database, where each record is numbered sequentially. You don't need to define the dimensions of a one-dimensional array. Well, I suppose you could, but why would you bother? Just keep writing line by line as the array expands. Then read through the records line by line. I suppose the records could be considered "ordered" in the sense that they are read sequentially.

 

[SadCeliac]

Maybe my issue is I just don't get what a record is??

 

[dav53521]

Maybe my issue is I just don't get what a record is??

A record has multiple different "variables" that can be of different types and each variables is accessed in the record by it's name.

An example record could be a student record which is declared in NESA pseudocode as (things between DIM and END should be indented)

DIM RECORD Student
Name as String (50)
Age as Integer
School as String (100)
Grade as Integer
TotalAverage as Real
END RECORD

And with this record a hypothetical student called Bob could have a record that would be structured like
Name: Bob Smith
Age: 17
School: James Ruse
Grade: 10
TotalAverage: 94.57

Also if you want to learn more you could (if you haven't already) look at the course specs as it's really helpful for stuff like the standard algorithms and the data structures used in SDD.

 

[SadCeliac]

A record has multiple different "variables" that can be of different types and each variables is accessed in the record by it's name.

An example record could be a student record which is declared in NESA pseudocode as (things between DIM and END should be indented)

DIM RECORD Student
Name as String (50)
Age as Integer
School as String (100)
Grade as Integer
TotalAverage as Real
END RECORD

And with this record a hypothetical student called Bob could have a record that would be structured like
Name: Bob Smith
Age: 17
School: James Ruse
Grade: 10
TotalAverage: 94.57

Also if you want to learn more you could (if you haven't already) look at the course specs as it's really helpful for stuff like the standard algorithms and the data structures used in SDD.

tysm!