How to find 0 is present in any bounding box?

I am having a problem...bbox in matlab are like [w,x,y,z] so is there any code which help me to check if any of one out these 4 variables are 0.

And also if I am having more than one bbox in single image...so is that valid or invalid?

Thanks in advance.

Answer 1

[Walter Roberson]

It is common to have more than one bounding box in an image. For example if you are tracking faces, then you would expect more than one bounding box if there were more than one face.

If you have a vector bbox that consists of [w,x,y,z] then to test if any of them are zero or negative,

any(bbox <= 0)

[Jyosh Matlab]

Thank you for the reply...

But I would like to ask in more detail...

I have a column name face (for example) now face contains bbox data...

like face(1) = [x, y, z, a] so can we check if any of these variable or value inside that boundary box is 0 or not...for column face and row 1 for this example. Can we check for whether any of x, y, z, a is 0 or not.

I hope now my question is more clear.

[Walter Roberson]

"I have a colum name face"

Assuming you mean that you have a table() in which there is a colum named face that is a series of cell entries each of which are 1 x 4, then:

face_mat = cell2mat(YourTable.face);
something_is_invalid = any(face_mat(:) <= 0);

and to find out which row is invalid:

invalid_idx = find(any(face_mat <= 0, 2));
something_is_invalid = ~isempty(invalid_idx);

[Jyosh Matlab]

Thanks I will try this and tell you.

[Jyosh Matlab]

This works but for cell where I have data of size m x 4 it divides that into m number of rows of each 1 x 4, and theres no way to turn back to original data...What to do?

[Walter Roberson]

cell2mat()

However, I might have been wrong about how your information was stored in the table.

Please try

[~, idx] = ismember('face', YourTable.Properties.VariableNames);
temp = struct(YourTable);
what_is_really_stored = temp.data{idx};
whos what_is_really_stored

and show us the answer.

[Jyosh Matlab]

What to write as Properties? My table name is trainData and variable is mine for example so what is

trainData.Properties.mine, what to replace properties with?

[Walter Roberson]

A = 123; B = 456; C = {'hello'};
T = table(A, B, C)

T = 1×3 table
     A      B         C    
    ___    ___    _________

    123    456    {'hello'}

struct(T)

Warning: Calling STRUCT on an object prevents the object from hiding its implementation details and should thus be avoided. Use DISP or DISPLAY to see the visible public details of an object. See 'help struct' for more information.

ans = struct with fields:
          propertyNames: {9×1 cell}
        defaultDimNames: {'Row'  'Variables'}
    dispRowLabelsHeader: 0
     emptyPropertiesObj: [1×1 matlab.tabular.TableProperties]
                   data: {[123]  [456]  {1×1 cell}}
                metaDim: [1×1 matlab.internal.tabular.private.metaDim]
                 rowDim: [1×1 matlab.internal.tabular.private.rowNamesDim]
                 varDim: [1×1 matlab.internal.tabular.private.varNamesDim]
             arrayProps: [1×1 struct]
                version: 4
                  ndims: []
                  nrows: []
               rownames: []
                  nvars: []
               varnames: []
                  props: []
        arrayPropsDflts: [1×1 struct]
             Properties: [1×1 matlab.tabular.TableProperties]

T.Properties

ans = 
  TableProperties with properties:

             Description: ''
                UserData: []
          DimensionNames: {'Row'  'Variables'}
           VariableNames: {'A'  'B'  'C'}
    VariableDescriptions: {}
           VariableUnits: {}
      VariableContinuity: []
                RowNames: {}
        CustomProperties: No custom properties are set.
      Use addprop and rmprop to modify CustomProperties.

ans = 1×3 cell array
    {'A'}    {'B'}    {'C'}

idx = 2

T.Properties.VariableNames
[~, idx] = ismember('B', T.Properties.VariableNames)

So we have a table() object, T. If you look at the struct(T) you will see that T has a property that is literally named Properties . You can look at what it holds -- fields such as DimensionNames. And a field literally named VariableNames . When you look at the Properties.VariableNames field of the table() object, you can see that it is a list of the names of the variables in the table. And you can use ismember() to find out what index (column number) a particular variable name is inside the table() object.

So you were not intended to substitute anything for "Properties" or "VariableNames": those were literal values. You were intended to do

[~, idx] = ismember('face', trainData.Properties.VariableNames)
temp = struct(trainData);
what_is_really_stored = temp.data{idx};
whos what_is_really_stored

However you seem to be saying now that your variable name is mine instead of face like you had said earlier. Instead of 'face' you should be using the name of whichever table variable holds your bounding boxes.

[Jyosh Matlab]

Thanks, you helped alot.

[Walter Roberson]

What results did you get?

The above is not intended as steps to fix the problem, the above is intended for you to tell us what the actual datatype is that is stored, so that we can give more correct code than we had above.

[Jyosh Matlab]

I'll let you know soon...right now I have not tested it yet.