This function test the precision of SpotFinderZ or SpotFinderF and indicates whether subpixel resolution was actually achieved. The function displays the distribution of spot position within pixel boundaries, plotting the global coordinates of the spots by modulus one. An approximately uniform distribution indicates that there was no tendency to pixel celters, a cluster in the middle inducates that there is such tendency and if subpixel resolution is desired, the "Shift limit" parameter of SpotFinderZ should be reduced.

  • <cellList> - an array that contains the spots. This could be either a "cellList" variable generated by SpotFinderZ, or a "spotList" variable generated by SpotFinderF. You can drag and drop the file with the data into MATLAB's workspace or open it using MATLAB's Import Tool.

  • <field> - field with the spots (if SpotFinderZ's cellList is used). Default: 'spots'.


This example uses the data set also used in the example for the SpotFinderF tool, which is an image of individual Cy5 fluorophores immobilized on a glass coverslip (courtesy of Dr. Sangjin Kim).

1. To start, run SpotFinderF as described in the example and obtain the spotList variable in the MATLAB's workspace. Notice that the value of the "Shift limit" parameter is set to 1. Don't close SpotFinderF after this run.

2. Now run the testspotprecision function:


Displayed spots

Here the distribution of the spots relative the pixels centers is close to uniform, indicating that the "Shift limit" does not affect the precision of the spot coordinates.

3. Set the "Shift limit" parameter to 5 leaving the rest of the parameters the same. Run the testspotprecision function again the same way.

Displayed spots

Here the distribution of the spots relative the pixels centers is not uniform, the detected spots cluster near pixels centers, indicating that the "Shift limit" affects the precision of the spot coordinates. Therefore, for precise measurements of spot positions, "Shift limit" must be set not higher than about 1.