Operator '==' is not supported for operands of type 'table'.

Question

Patrick Lonergan 2021-8-6

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https://ww2.mathworks.cn/matlabcentral/answers/893812-operator-is-not-supported-for-operands-of-type-table

评论： Patrick Lonergan 2021-8-7

I am tyring to extract each ID for the table attached in the image (table is really large so did not attach the whole table). My code is as follows but I continue to get this error "Operator '==' is not supported for operands of type 'table'." when

A=[c];
R=c(:,"SAPID")
T=transpose(1:127)
u=(unique(R))
TurbineTest1=A(A.SAPID==u(1,1),:);
TurbineTest2=A(A.SAPID==u(2,1),:);
TurbineTest3=A(A.SAPID==u(3,1),:);
TurbineTest4=A(A.SAPID==u(4,1),:);
TurbineTest5=A(A.SAPID==u(5,1),:);
TurbineTest6=A(A.SAPID==u(6,1),:);
TurbineTest7=A(A.SAPID==u(7,1),:);

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Answer 1

Scott MacKenzie 2021-8-6

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Try this:

TurbineTest1=A(strcmp(A.SAPID,u(1,1)),:);

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Answer 2

Peter Perkins 2021-8-6

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There are a couple of problems. c is a table, so

R = c(:,"SAPID")

is also a table, with only one variable. A table is a container, so

u = unique(R)

isn't going to work, and even if it did,

A.SAPID == u(1,1)

wouldn't. You want

u = unique(A.SAPID)

Then unique works, and == works. But wait, A.SAPID is a cell array of char, so == is still not going to work. As Scott suggests, you can use strcp. But I'd recommend using a string array for text data, not cell. It might be as simple as using "TextType","string" when you import data.

BUT ACTUALLY, values in SAPID appear to be drawn from a finite set of choices, in other words, they are categorical data. You probably should be using a categorical array.

A.SAPID = categorical(A.SAPID);

Then, all you need to do is iterate over categories(A.SAPID). == just works.

u = categories(A.SAPID);
TurbineTest1 = A(A.SAPID==u(1),:);

BUT HANG ON. Do you really want maybe dozens of separate tables in your workspace? I strongly recommend that you look at things like groupsummary and rowfun to see if you can do operations on groups in your data without pulling it apart.