anonymous function w/ accumarray

2021 7 1
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更新时间：2022 8 22
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tdata = table([ 1 1 1 2 2]', [1 5 9 10 1]', 'VariableNames',{'year','id'})
Hi
I got error message below. Could you help shed light why I can't use accumarray with concatinating text output?
year id
____ __
1 1
1 5
1 9
2 10
2 1
cat = @(x) {sprintf([repmat('%s,',1,length(x)-1) '%s'], string(x))};
However got error below when trying to call
[ uniqYr,~,JGrp] = unique( tdata(:,'year'));
tt= accumarray( JGrp, tdata.id, [], @cat);
Error using cat
Dimension argument must be a real, positive, integer scalar.

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 采纳的回答

Star Strider
Star Strider 2021-7-1
Ran in:

0 个投票

Ran in:
Naming your function ‘cat’ overshadows the existing MATLAB function by that name, that you inadvertently called when you used the ‘@’ operator in the accumarray call. First, rename the anonymous function, and do not use the ‘@’ in the accumarray call when calling it, since it is already a function handle.
This slight variation on the original code works:
tdata = table([ 1 1 1 2 2]', [1 5 9 10 1]', 'VariableNames',{'year','id'})
tdata = 5×2 table
year id ____ __ 1 1 1 5 1 9 2 10 2 1
catfcn = @(x) {sprintf([repmat('%s,',1,length(x)-1) '%s'], string(x))};
[ uniqYr,~,JGrp] = unique( tdata(:,'year'));
tt= accumarray( JGrp, tdata.id, [], catfcn)
tt = 2×1 cell array
{'1,5,9'} {'10,1' }
.

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Star Strider
Star Strider 2021-7-1
As always, my pleasure!
Pete sherer
Pete sherer 2022-8-22
How can i do this operation with the string type variable? say another variable is "name" with values
tdata = table([ 1 1 1 2 2]', [1 5 9 10 1]',["a" "b" "c" "d" "e"]', 'VariableNames',{'year','id','name'})
then the accumarray should return
accumarray( JGrp, tdata.name, [], catfcn)
{'a,b,c}
{d,e}
Star Strider
Star Strider 2022-8-22
Ran in:
Ran in:
The accumarray function only works with numeric values and character vectors, so your example code requires one small change —
tdata = table([ 1 1 1 2 2]', [1 5 9 10 1]',['a' 'b' 'c' 'd' 'e']', 'VariableNames',{'year','id','name'})
tdata = 5×3 table
year id name ____ __ ____ 1 1 a 1 5 b 1 9 c 2 10 d 2 1 e
catfcn = @(x) {sprintf([repmat('%s,',1,length(x)-1) '%s'], string(x))};
[ uniqYr,~,JGrp] = unique( tdata(:,'year'));
tt = accumarray( JGrp, tdata.name, [], catfcn)
tt = 2×1 cell array
{'a,b,c'} {'d,e' }
Then, it works!
.
Pete sherer
Pete sherer 2022-8-22
编辑：Pete sherer 2022-8-22
I tried using the cellstr() to apply to the string-type variable before using the step above but it didn't work.
tdata = table([ 1 1 1 2 2]', [1 5 9 10 1]',["a" "b" "c" "d" "e"]', 'VariableNames',{'year','id','name'});
tdata.name= cellstr( tdata.name);
catfcn = @(x) {sprintf([repmat('%s,',1,length(x)-1) '%s'], string(x))};
[ uniqYr,~,JGrp] = unique( tdata(:,'year'));
tt = accumarray( JGrp, tdata.name, [], catfcn)
Error using accumarray
Second input VAL must be a full numeric, logical, or char vector or scalar.
Star Strider
Star Strider 2022-8-22
Ran in:
Ran in:
It doesn’t work because it remains a cell array. Use the char function instead —
tdata = table([ 1 1 1 2 2]', [1 5 9 10 1]',["a" "b" "c" "d" "e"]', 'VariableNames',{'year','id','name'});
% tdata.name= cellstr( tdata.name)
tdata.name = char(tdata.name)
tdata = 5×3 table
year id name ____ __ ____ 1 1 a 1 5 b 1 9 c 2 10 d 2 1 e
catfcn = @(x) {sprintf([repmat('%s,',1,length(x)-1) '%s'], string(x))};
[ uniqYr,~,JGrp] = unique( tdata(:,'year'));
tt = accumarray( JGrp, tdata.name, [], catfcn)
tt = 2×1 cell array
{'a,b,c'} {'d,e' }
.

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