How to reorder columns and array elements based on an array?

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Corymbiamaculata 2024-2-21

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https://ww2.mathworks.cn/matlabcentral/answers/2084863-how-to-reorder-columns-and-array-elements-based-on-an-array

评论： Dyuman Joshi 2024-2-25

I'm working with a 1000x20 matrix containing weight measurements of 20 different species, ordered alphabetically. I want to plot mean weight measurements 1) separately for each species (so 20 elements), and 2) grouped based on various characteristics, like the biome (so 2-4 elements).

I created a 1x20 string with all species names (used in tick labels), and then arrays with column indices corresponding to various species, like this:

all_species = 1:20;
species_groups.biome1 = [5 6 8 10 11 12 16];                            % species in biome 1
species_groups.biome2 = setdiff(all_species,species_groups.biome1);     % species in biome 2

This way, I'm able to easily define input data for various figures and plot the mean weight of whichever species I want.

Now I want to change the order of species in the figure where each species is plotted separately - or preferably, in the entire dataset before any analysis is done. I have a new 1x20 string with the desired order:

new_order = [14 13 15 12 16 4 3 5 6 8 9 7 1 2 17 18 19 20 10 11];

What's the easiest way to:

1) reorder the columns in my original 1000x20 dataset based on this array, so that e.g. the species that was 14th in the original dataset would instead come first?

2) Replace all the numbers (in fact column indices) in species_groups with corresponding values from the new_order array?

Many thanks in advance for help!

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Answer 1

Dyuman Joshi 2024-2-21

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https://ww2.mathworks.cn/matlabcentral/answers/2084863-how-to-reorder-columns-and-array-elements-based-on-an-array#answer_1413518

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"1) reorder the columns in my original 1000x20 dataset based on this array, so that e.g. the species that was 14th in the original dataset would instead come first?"

Directly use those indices -

all_species = 1:20;
species_groups.biome1 = [5 6 8 10 11 12 16];                            % species in biome 1
species_groups.biome2 = setdiff(all_species,species_groups.biome1);     % species in biome 2
species_groups
species_groups = struct with fields:
    biome1: [5 6 8 10 11 12 16]
    biome2: [1 2 3 4 7 9 13 14 15 17 18 19 20]
new_order = [14 13 15 12 16 4 3 5 6 8 9 7 1 2 17 18 19 20 10 11];
data = data(:,new_order);

"2) Replace all the numbers (in fact column indices) in species_groups with corresponding values from the new_order array?"

Once again, indexing ftw -

species_groups.biome1 = new_order(species_groups.biome1);     % species in biome 1
species_groups.biome2 = new_order(species_groups.biome2);     % species in biome 2
species_groups
species_groups = struct with fields:
    biome1: [16 4 5 8 9 7 18]
    biome2: [14 13 15 12 3 6 1 2 17 19 20 10 11]