Hi I spoke to someone and eventually figured it out so thank for your reply anyway. The data is stored in a cell array and i had a push button to select the data. But the problem was in defining the string to be used and not putting the correct thing in the callback part of the code. The code below is what seems to work.
% --- Executes on button press in pushbutton3.
function pushbutton3_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton3 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Extract curve information
ci = handles.wlog.curve_info(2:end, 1);
handles.ci = ci;
% Update handles structure
guidata(handles.figure1, handles);
% Set popupmenu1 string for list
set(handles.popupmenu1,'string',ci)
% --- Executes on selection change in popupmenu1.
function popupmenu1_Callback(hObject, eventdata, handles)
% hObject handle to popupmenu1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: contents = cellstr(get(hObject,'String')) returns popupmenu1 contents as cell array
% contents{get(hObject,'Value')} returns selected item from popupmenu1
%data = evalin('base','ci');
data = guidata(handles.figure1);
set(hObject, 'String', data.handles.ci)
% --- Executes during object creation, after setting all properties.
function popupmenu1_CreateFcn(hObject, eventdata, handles)
% hObject handle to popupmenu1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: popupmenu controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end