How to lookup and return a corresponding value from table?

67 ビュー (過去 30 日間)
deepak kumar
deepak kumar 2021 年 12 月 27 日
コメント済み: deepak kumar 2021 年 12 月 28 日
I have a table the first column of which contains a string and other columns contain numeric data, how do I match the string and return the corresponding values form other columns for this string. Lets say for 'obs2' I want '2' as output. I am using following code but this isn't working.
cmnt0 = {'obs1';'obs2';'obs3';'obs4'};
curve=[1;2;3;2];
cmnt1 = table(cmnt0,curve,'VariableNames',{'obs','Curve'})
cmnt1 = 4×2 table
obs Curve ________ _____ {'obs1'} 1 {'obs2'} 2 {'obs3'} 3 {'obs4'} 2
for i=[1,2,3,4]
x=strcmp(cmnt1(i,1),'obs1')
if x==1
%% some code here after that
end
end
x = logical
0
x = logical
0
x = logical
0
x = logical
0

採用された回答

Voss
Voss 2021 年 12 月 27 日
編集済み: Voss 2021 年 12 月 27 日
It isn't working because cmnt1(i,1) is a sub-table of the table cmnt1 that contains one cell of cmnt1. You want to refer to the contents of the cell directly, so use curly brace indexing:
cmnt0 = {'obs1';'obs2';'obs3';'obs4'};
curve=[1;2;3;2];
cmnt1 = table(cmnt0,curve,'VariableNames',{'obs','Curve'})
cmnt1 = 4×2 table
obs Curve ________ _____ {'obs1'} 1 {'obs2'} 2 {'obs3'} 3 {'obs4'} 2
% introduce a third column for demonstration:
cmnt1.Curve_2 = [5;6;7;8]
cmnt1 = 4×3 table
obs Curve Curve_2 ________ _____ _______ {'obs1'} 1 5 {'obs2'} 2 6 {'obs3'} 3 7 {'obs4'} 2 8
for i=[1,2,3,4]
% x=strcmp(cmnt1(i,1),'obs1')
x=strcmp(cmnt1{i,1},'obs1')
if x==1
%% some code here after that
output = cmnt1{i,2:end} % do this to store the contents of the cells in columns 2 to the end (which are all numeric), or
output = cmnt1{i,2} % do this to store the contents of the cell in column 2
end
end
x = logical
1
output = 1×2
1 5
output = 1
x = logical
0
x = logical
0
x = logical
0
You can do the same thing without a loop, using logical indexing, which is intended to also handle the situation where the string you are matching occurs more than once in the first column of the table:
% introduce a second 'obs1':
cmnt1{3,1} = {'obs1'}
cmnt1 = 4×3 table
obs Curve Curve_2 ________ _____ _______ {'obs1'} 1 5 {'obs2'} 2 6 {'obs1'} 3 7 {'obs4'} 2 8
is_match = strcmp(cmnt1{:,1},'obs1')
is_match = 4×1 logical array
1 0 1 0
output_array = cmnt1{is_match,2:end}
output_array = 2×2
1 5 3 7
output_subtable = cmnt1(is_match,2:end)
output_subtable = 2×2 table
Curve Curve_2 _____ _______ 1 5 3 7
  1 件のコメント
deepak kumar
deepak kumar 2021 年 12 月 28 日
thank you for support. Your answer helped.
But containers.Map are the exact thing I was looking for.

サインインしてコメントする。

その他の回答 (1 件)

dpb
dpb 2021 年 12 月 27 日
I'd start by turning 'obs' into a categorical variable...
cmnt0 = categorical({'obs1';'obs2';'obs3';'obs4'});
curve=[1;2;3;2];
tC = table(cmnt0,curve,'VariableNames',{'Obs','Curve'});
...
C=t.Curve(t.Obs=='Obs1');
Alternatively, if there is some reason to not create the categorical variable, then
C=t.Curve(contains(t.Obs,{'Obs1'}));
With such a data set, I'd suggest you'll find that groupsummary and/or rowfun and friends with grouping variables will solve virtually all such problems almost automagically.
  3 件のコメント
dpb
dpb 2021 年 12 月 27 日
" avoid CONTAINS..."
Good point...why I would use categorical variables here.

サインインしてコメントする。

カテゴリ

Find more on Tables in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by