DSP – Filtering in the frequency domain via FFT

There are two issues: the way you use the FFT, and the particular filter. Filtering is traditionally implemented as convolution in the time domain. You’re right that multiplying the spectra of the input and filter signals is equivalent. However, when you use the Discrete Fourier Transform (DFT) (implemented with a Fast Fourier Transform algorithm for … Read more

Filtering with checkboxes using jQuery

I think the two most straightforward approaches would be on click of any of the filter checkboxes either: Hide all <div> elements, then loop through the checkboxes and for each checked one .show() the <div> elements with the associated category. Loop through all checkboxes to make a list of the classes to be shown, then … Read more

Pandas- Select rows from DataFrame based on condition

I think you need boolean indexing: df1 = df[(df[‘category’] == ‘A’) & (df[‘value’].between(10,20))] print (df1) category value 2 A 15 4 A 18 And then: df2 = df[(df[‘category’] != ‘A’) & (df[‘value’].between(10,20))] print (df2) category value 1 B 10 Or: df3 = df[df[‘category’] != ‘A’] print (df3) category value 1 B 10 3 B 28 … Read more

Changing values from Cursor using SimpleCursorAdapter

The simplest way to format a cursor value is to use SimpleCursorAdapter.setViewBinder(..): SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.list, cursor, new String[] { Definition.Item.TITLE, Definition.Item.CREATE_DATE }, new int[] { R.id.title, R.id.createDate}); adapter.setViewBinder(new ViewBinder() { public boolean setViewValue(View aView, Cursor aCursor, int aColumnIndex) { if (aColumnIndex == 2) { String createDate = aCursor.getString(aColumnIndex); TextView textView = (TextView) … Read more

Partial search in HashMap

Yeah, a HashMap is not the right data structure for this. As Bozho said, a Trie would be the right one. With Java’s on-board tools, a TreeMap (or any SortedMap, actually) could be used: public <V> SortedMap<String, V> filterPrefix(SortedMap<String,V> baseMap, String prefix) { if(prefix.length() > 0) { char nextLetter = prefix.charAt(prefix.length() -1) + 1; String … Read more