How to convert cell array into double in table

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Bharath
Bharath 2016-4-4
回答： Peter Perkins 2017-3-31
Hi all, I've a table of the format
section D1 D2 L sectionID
____________________ ____ _____ _____ _________
1.00000000000000e+00 [ 5] [ 5] [ 6] [11]
2.00000000000000e+00 [12] [ 2] [ 34] [11]
3.00000000000000e+00 [12] [312] [323] [11]
4.00000000000000e+00 [ 3] [ 45] [ 23] [11]
5.00000000000000e+00 [ 4] [ 4] [ 23] [11]
6.00000000000000e+00 [ 2] [ 43] [ 23] [11]
7.00000000000000e+00 [ 3] [ 4] [ 23] [11]
8.00000000000000e+00 [ 4] [ 23] [ 32] [11]
Where Section is a double and rest D1,D2,L and section ID are cell arrays. I want to convert all these too into double arrays. I tried to do using cell2mat
temp_table.D1 = cell2mat(temp_table.D1);
temp_table.D2 = cell2mat(temp_table.D2);
temp_table.L = cell2mat(temp_table.L);
temp_table = cell2mat(temp_table.sectionID);
When I try to use the cell2mat in the above way, I get the following error
Field assignment to a non-structure array object.
Struct contents reference from a non-struct array object.
Error in sample_gui_ver2/tb9_Callback (line 1918)
temp_table.D1 = cell2mat(temp_table.D1);
Error while evaluating UIControl Callback
Can anyone help me to fix this issue. Thanks in advance.

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回答（4 个）

Peter Perkins
Peter Perkins 2017-3-31
This whole thread begs the question of how the table got like that to begin with, which is worth you figuring out, probably. But I think what you're looking for is
>> t = table([1;2;3;4],{5;6;7;8},{9;10;11;12},[13;14;15;16])
t =
4×4 table
Var1 Var2 Var3 Var4
____ ____ ____ ____
1 [5] [ 9] 13
2 [6] [10] 14
3 [7] [11] 15
4 [8] [12] 16
>> for i = 1:width(t), if iscell(t.(i)), t.(i) = cell2mat(t.(i)); end, end
>> t
t =
4×4 table
Var1 Var2 Var3 Var4
____ ____ ____ ____
1 5 9 13
2 6 10 14
3 7 11 15
4 8 12 16
Alternatively, if all the vars in thetable are cells, use varfun:
>> t = table({1;2;3;4},{5;6;7;8},{9;10;11;12},{13;14;15;16})
t =
4×4 table
Var1 Var2 Var3 Var4
____ ____ ____ ____
[1] [5] [ 9] [13]
[2] [6] [10] [14]
[3] [7] [11] [15]
[4] [8] [12] [16]
>> t = varfun(@cell2mat,t)
t =
4×4 table
cell2mat_Var1 cell2mat_Var2 cell2mat_Var3 cell2mat_Var4
_____________ _____________ _____________ _____________
1 5 9 13
2 6 10 14
3 7 11 15
4 8 12 16
and then patch up the names. varfun is a bit less convenient when only some vars are cells, you'd end up having to interleave two pieces back together.
Will Wilson
Will Wilson 2017-3-29
Try using str2double to get the job done. Something like this:
temp_table.D1 = str2double (temp_table.D1);
Walter Roberson
Walter Roberson 2017-3-29
Notice that the error is
Field assignment to a non-structure array object.
The problem is the destination being assigned to, not the source. At some line above what you show, you have assigned a non-structure to temp_table, such as a numeric array, and then the assignment to temp_table.D1 is trying to treat the existing object as if it were a structure. Instead of just erasing all of the existing temp_table and creating a new structure, MATLAB complains that it is not already a structure.
The problem would not occur if temp_table were a structure (or table), or if temp_table did not exist at that point.
Azzi Abdelmalek
Azzi Abdelmalek 2016-4-4
Probably one of the columns is not a cell array. Check if all columns are cell array

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