CODEWITHSUNDEEP
javaarraysmultidimensional-arrayarraylistdouble
ukbaz
ukbaz

Reputation: 547

Calling 2D Array Function ''Cannot Convert Double[][] To Double" Error

hope everyone is well.

I am getting this error when calling a method that I've created. I reason why I created the method is to return 2 double values, so I used a 2d array. Here is my relevant code: 

Double[][] type2FS;
type2FS = new Double[rule.getRules().get(x).getAttributes().size()][rule.getRules().get(x).getAttributes().size()];
int pos=0;

the 2d array is the size of the number of attributes in a Decision Tree Rule, the rules are stored in an ArrayList.

type2FS[pos][pos]=calRight(grade.getDM(),grade.getDNU(),grade.getDNL(),Double.parseDouble(store.getData()[i][z]));
pos++;
break;

I get the error in the part after the '=' sign, with the message "Type mismatch: cannot convert from Double[][] to Double". There are 4 double variables that are passed.

private Double[][] calRight(double dm, double dnu, double dnl, double value) 
    {
    double upperMg= (value-dnl) / (dnu-dnl);
    double lowerMg= 1 - upperMg;

    if(upperMg>1.0)
    {
        upperMg=1.0;    
    }
    else if (upperMg<0.0)
    {
        upperMg=0.0;
    }

    if(lowerMg>1.0)
    {
        lowerMg=1.0;
    }
    else if(lowerMg<0.0)
    {
        lowerMg=0.0;
    }
    Double[][] temp = {{upperMg},{lowerMg}};
    return temp;
}

This is the method that calculates the 2 double values that I wish to store in my type2FS 2D array.

The 2 double values that are returned from the function are part of a set. So one set looks like (4.5,5.5), now one decision tree rule can have many sets depending on the rule. So I thought the best way to store this was in a 2D Array.

I cant understand where I'am going wrong. Any help would be greatly appreciated.

Thank you

Upvotes: 0

Views: 270

Answers (3)

Luigi Cortese
Luigi Cortese

Reputation: 11131

type2FS[pos][pos] = ...

is trying to assing a value to a single "cell" of your array, so it should be a double value. But you're passing an array instead.

So, change 

type2FS[pos][pos]=calRight(grade.getDM(),grade.getDNU(),grade.getDNL(),Double.parseDouble(store.getData()[i][z]));

to

type2FS=calRight(grade.getDM(),grade.getDNU(),grade.getDNL(),Double.parseDouble(store.getData()[i][z]));

Anyway, "[...] to return 2 double values, so I used a 2d array" doesn't make sense, you could use a 1d array as well:

private Double[] calRight(double dm, double dnu, double dnl, double value) {
    //other code
    Double[] temp = {upperMg,lowerMg};
    return temp;
}

even though that's not the best solution anyway.

Upvotes: 1

Subhrajyoti Majumder
Subhrajyoti Majumder

Reputation: 41210

Error - 'Cannot Convert Double[][] To Double"

yes it, why! type2FS[pos][pos] is double type reference & calRight(...) returns double[][]. It is type mismatch.

type2FS[pos][pos]=calRight(grade.getDM(),grade.getDNU(),grade.getDNL(),Double.parseDouble(store.getData()[i][z]));

Upvotes: 1

Siva Kumar
Siva Kumar

Reputation: 2006

type2FS[pos][pos]=calRight(grade.getDM(),grade.getDNU(),grade.getDNL(),Double.parseDouble(store.getData()[i][z]));

It means i value is pos and j value is pos , then you are going to assign particular row and and column value then its boolean.

instead of that 

type2FS =calRight(grade.getDM(),grade.getDNU(),grade.getDNL(),Double.parseDouble(store.getData()[i][z]))

you can call like that.

type2FS[pos] is expecting one dimension array. Because you are mentioning only row.

type2FS[pos][[pos] is expecting Double value. Because you are mentioning row ans column.

Upvotes: 1

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