Adding a datapoint to datastruct in matlab - matlab

Question

I am trying to add a datapoint to an existing data struct. I have created the following data struct.
ourdata.animal= {'wolf', 'dog', 'cat'}
ourdata.height = [110 51 32]
ourdata.weight = [55 22 10]
say I want to add another one to the data struct with name 'fish' height 3 and weight 1, how do I go about this?

Answer 1

You can simply attach it to the end of the structure:
ourdata.animal{end+1} = 'fish'
ourdata.height(end+1) = 3
ourdata.weight(end+1) = 1

Answer 2

If you want to work with multiple structures, you can write a little function to combine the values of fields in multiple structs. Here's one, using fieldnames() to discover what fields exist:
function out = slapItOn(aStruct, anotherStruct)
% Slap more data on to the end of fields of a struct
out = aStruct;
for fld = string(fieldnames(aStruct))'
out.(fld) = [aStruct.(fld) anotherStruct.(fld)];
end
end
Works like this:
>> ourdata
ourdata =
struct with fields:
animal: {'wolf' 'dog' 'cat'}
height: [110 51 32]
weight: [55 22 10]
>> newdata = slapItOn(ourdata, struct('animal',{{'bobcat'}}, 'height',420, 'weight',69))
newdata =
struct with fields:
animal: {'wolf' 'dog' 'cat' 'bobcat'}
height: [110 51 32 420]
weight: [55 22 10 69]
>>
BTW, I'd suggest that you use string arrays instead of cellstrs for storing your string data. They're better in pretty much every way (except performance). Get them with double quotes:
>> strs = ["wolf" "dog" "cat"]
strs =
1×3 string array
"wolf" "dog" "cat"
>>
Also, consider using a table array instead of a struct array for tabular-looking data like this. Tables are nice!
>> animal = ["wolf" "dog" "cat"]';
>> height = [110 51 32]';
>> weight = [55 22 10]';
>> t = table(animal, height, weight)
t =
3×3 table
animal height weight
______ ______ ______
"wolf" 110 55
"dog" 51 22
"cat" 32 10
>>